CN116744857A

CN116744857A - Equalization of matrix-based line imagers for ultrasound imaging systems

Info

Publication number: CN116744857A
Application number: CN202280011455.6A
Authority: CN
Inventors: 优素福·哈克; 桑迪普·阿卡拉杰; 雅努什·布雷泽克; 安达利布·乔杜里
Original assignee: Exo Imaging Inc
Current assignee: Exo Imaging Inc
Priority date: 2021-01-22
Filing date: 2022-01-13
Publication date: 2023-09-12
Also published as: IL304558A; US20220233168A1; CA3206088A1; KR20230130121A; US20230200781A1; JP2024504374A; WO2022159327A1; US11504093B2; TW202234085A; EP4280963A1

Abstract

Disclosed herein is an ultrasound transducer system comprising: an ultrasound imager comprising a plurality of pMUT transducer elements; and one or more circuits electronically connected to the plurality of transducer elements, the one or more circuits configured to enable pulsed emission of the ultrasound transducer and reception of the reflected signal, wherein the inductor is used to equalize the impedance to obtain a greater pressure output. Also disclosed are methods of varying the pressure of ultrasonic waves emitted by an ultrasonic transducer.

Description

Equalization of matrix-based line imagers for ultrasound imaging systems

Cross reference

The present application is a continuation of U.S. patent application Ser. No. 17/156,058, filed on 1/22 of 2021, the contents of which are incorporated herein by reference in their entirety.

Background

For ultrasound imaging, a transducer is used to transmit an ultrasound beam to a target to be imaged, and reflected waveforms are received by the transducer. The received waveforms are converted into electrical signals and, through further signal processing, ultrasound images are generated. Traditionally, for two-dimensional (2D) imaging, an ultrasound transducer includes a one-dimensional (1D) transceiver array for transmitting ultrasound beams. It is desirable to generate a high pressure level in the transmitted ultrasound beam.

SUMMARY

Piezoelectric sensors have been used for medical imaging for over twenty years. These piezoelectric sensors are typically constructed using bulk piezoelectric films (bulk piezoelectric films). These films form piezoelectric elements arranged in columns in the azimuth direction. Each column may be driven by a firing driver. By using different time delays on successive columns, the transmitted beam can be focused in the azimuth direction.

The elevation arrangement of the array of piezoelectric elements may allow the beams of the array to be electronically focused into a narrow beam in the elevation plane. A single row of piezoelectric elements of the transceiver array is unable to achieve electronic focusing in the elevation or thickness dimension of the 2D ultrasound image. Conventional 2D ultrasound images have a thickness in the azimuth plane, in the elevation direction (i.e., conventional techniques for confining a beam to a thin image slice mechanically focus the beam in the lateral or elevation dimension by contouring the piezoelectric element in that dimension or lensing each element). The 2D array of transducers may be arranged such that elements in the elevation direction allow for electronic focusing in the elevation direction, while also allowing for azimuthal electronic focusing traditionally done in existing legacy systems.

For optimal power transfer from an input source to another circuit, the output impedance of the source should be the complex conjugate of the input impedance of the circuit it drives. In particular, in the best case, the real parts of the two impedances should be equal and the complex parts should be complex conjugates of each other. Transducers implemented using piezoelectric micromachined ultrasonic transducers (pmuts) are highly capacitive in nature. For a transmit driver attempting to transmit an ultrasound signal into tissue, the impedance of the driver needs to be matched to the input impedance of the transducer as described above. However, pMUT-based transducers are highly capacitive, which requires that an inductor be used in series with the source driver to maximize the power delivered to the transducer.

In one aspect, an ultrasound imaging system including a transducer is disclosed. The transducer includes at least one transducer element. Each transducer element has two terminals. The at least one transducer element is in a transmit mode. The transducer also includes at least one transmit driver. Each transmit driver is connected to each first terminal of at least one transducer element. The transducer further comprises at least one inductor comprising two terminals. Each first terminal of each inductor is connected to each second terminal of each transducer element. Each second terminal of each inductor is connected to a bias voltage.

In some embodiments, the transducer is a piezoelectric micromachined transducer (pMUT) device.

In some embodiments, the transducer is a capacitive micromachined ultrasonic transducer (cMUT) device or a bulk piezoelectric transducer (bulk piezo transducer).

In some embodiments, the at least one transducer element is a plurality of transducer elements organized in an array.

In some embodiments, the array is organized into rows and columns. A plurality of transducer elements in a column are electronically selected to define a column of transducer elements.

In some embodiments, a plurality of transducer elements in a row are electronically selected to define a row of transducer elements.

In some embodiments, the delays of the transducer elements in the first column are independent of the delays of the transducer elements in the second column, and the delays of the transducer elements in the first row are independent of the delays of the transducer elements in the second row.

In some embodiments, the transducer elements on a column have different delays.

In some embodiments, the bias voltage is selected from the group consisting of a ground voltage, a negative voltage, and a positive voltage.

In some embodiments, the bandwidth of the transducer is increased in the region of interest.

In some embodiments, at least one value of at least one inductor is selected to provide an increase in pressure output over a frequency range of interest.

In some embodiments, at least one value of the at least one inductor is selected to be large enough to cancel a phase change introduced by at least one capacitance of the at least one transducer element.

In some embodiments, the bandwidth of the transducer is controlled by selecting a plurality of transducer elements on a column.

In some embodiments, the pressure output of the selected transducer element is adjusted by varying a plurality of voltage drive levels of a plurality of transmit drivers of the selected transducer element.

In some embodiments, the voltage drive level is changed using multi-level transmit drive pulses and selecting a desired digital drive level.

In some embodiments, the voltage drive level is further controlled using pulse width modulation of the transmit pulsar (pulsar) waveform.

In some embodiments, the transducers are configured to provide electronic control of elevation focus (elevation focus) in the elevation direction along the column.

In some embodiments, the transducer elements along a column are driven by multi-level (multilevel) pulses.

In some embodiments, the transducer elements on a column are driven by a multi-level pulse train.

In some embodiments, the pulse amplitude, width, shape, pulse frequency, and combinations thereof of the multi-level pulses in the multi-level pulse train are electrically programmable.

In some embodiments, the delay of the start of the multi-level pulse is electrically programmable.

In some embodiments, the delays of the elements indexed by row and column are calculated by summing the delays of the columns with the delays of the rows.

In some embodiments, the delay may be a sum of a coarse delay (coarse delay) and a fine delay (fine delay).

In some embodiments, the delay of the start of the pulse is programmable in the X-direction.

In some embodiments, the delay of the start of the pulse is programmable in the Y direction.

In some embodiments, the shape of the multi-level pulse is selected from the group consisting of sinusoidal and digital square waves.

In some embodiments, the transmit driver is configured to drive one or more transducer elements along a column. The transmit driver is driven by a signal from the transmit channel. The signal of the transmit channel is electronically delayed relative to delays applied to other transmit channels driving other transducer elements on different columns.

In some embodiments, one or more transducer elements along a column operate with substantially the same delay.

In some embodiments, the transmit channel and the additional transmit channel are configured to electrically control a relative delay between adjacent columns. The control circuit is configured to set the relative delays of the first number of transducer elements on the columns such that the first number of transducer elements in the same row shares substantially the same relative delays as the second number of transducer elements of the starting row.

In some embodiments, the transducer elements of the plurality of transducer elements include a top portion, a center portion, and a bottom portion, each of which includes a plurality of rows and columns for pulsed transmission and reception of reflected ultrasonic signals. The pulsed emission from the top, center and bottom portions and the reception of the reflected ultrasonic signals are used to focus the reflected ultrasonic signals in the azimuth direction using a first beamformer. Elevation focusing is achieved using a second beamformer.

In some embodiments, the focal length in the elevation direction is electronically programmed.

In some embodiments, both the pulsed emission of the top and bottom portions and the reception of the reflected signal are performed simultaneously.

In some embodiments, the transducer elements perform parallel beamforming to produce a plurality of scan lines.

In some embodiments, two adjacent transducer elements on one of the one or more rows are addressed together, and wherein the transducers of the plurality of transducer elements comprise a top portion, a center portion, and a bottom portion, each of which includes a first number of rows and a second number of columns for ultrasound pulse transmission and reception of reflected ultrasound signals. The ultrasonic pulse transmissions from these portions and the receipt of the reflected ultrasonic signal are used to focus the reflected ultrasonic signal in the azimuth direction using a first beamformer. Elevation focusing is achieved using a second beamformer. For imaging using B-mode, the receive channel is assigned to two transducer elements on the same row, one from the top portion and the other from the bottom portion, and the other channel is assigned to two transducer elements of the center portion.

In some embodiments, 2N receive channels are used to address N columns.

In some embodiments, during transmit operation, all of the plurality of transducer elements electronically selected are operated on to generate pressure with elevation focus. In a receive operation, all of the plurality of transducer elements selected electronically individually are used to reconstruct an image focused in both the azimuth and elevation planes.

In some embodiments, the ultrasound imaging system further comprises a control circuit configured to electrically control the relative delays along the columns as a sum of the linear delays and any fine delays.

In some embodiments, the linear delays and any fine delays of a column are independent of the other linear delays and any fine delays of other columns of transducers, allowing for arbitrary steering and focusing in three dimensions.

In some embodiments, each transducer element exhibits multiple vibration modes, wherein only one vibration mode is triggered when the frequency band of the input stimulus is limited to a frequency less than the adjacent mode.

In some embodiments, each transducer element exhibits a plurality of vibration modes, wherein frequencies generated from the first vibration mode overlap with frequencies generated from the second vibration mode.

In some embodiments, each transducer element exhibits multiple vibration modes simultaneously when driven by a broadband frequency input including a center frequency.

In one aspect, an ultrasound imaging system including an ultrasound transducer is disclosed. The transducer includes a bias voltage. The transducer also includes a column of transducer circuits. The transducer circuit includes a transducer element including a transducer for converting an electrical signal into ultrasonic waves. The transducer element has a first terminal and a second terminal. The transducer further comprises a circuit comprising an input drive device for providing an electrical potential to the transducer element, the input drive device being connected to the first terminal of the transducer element. The transducer further includes an inductor connected to the second terminal of the transducer element. The transducer also includes a switch for connecting the transducer circuit to a bias voltage.

In some embodiments, the ultrasound transducer is a pMUT device.

In some embodiments, the ultrasound transducer is a cMUT device or a bulk piezoelectric transducer.

In some embodiments, the ultrasound imaging system further comprises a switch connected in parallel with the inductor for the purpose of shorting the inductor.

In some embodiments, the ultrasound imaging system includes multiple columns.

In some embodiments, one of the columns includes an inductor connected in series with the transducer element.

In some embodiments, the ultrasound imaging system further comprises an inductor connected in series between the multi-column transducer circuit and the bias voltage.

In some embodiments, the transducer element is configured to transmit a signal comprising a delay.

In some embodiments, one or more transducer elements on a column operate with different delays.

In some embodiments, the delay profile (delay profile) that includes delays from one or more transducer elements having a common column index is symmetrical.

In some embodiments, the delay is the sum of a coarse delay and a fine delay.

In some embodiments, the coarse delay is linear between one or more adjacent transducer elements.

In some embodiments, the delays of transducer elements having a column index and a row index are the sum of a column delay, a linear coarse row delay, and a fine row delay.

In one aspect, a method for increasing the pressure of ultrasonic waves emitted by a transducer comprising at least one transducer element. The method includes placing at least one transducer element in a transmit mode using at least one transmit driver connected to the at least one transducer element. Each transducer element has a first terminal and a second terminal. The method further comprises the steps of: for at least one inductor, a first terminal of each of the at least one inductor is connected to a second terminal of each transducer element. The second terminal of the at least one inductor is connected to a bias voltage. The at least one inductor is not integrated with the transducer element. The transducer further includes each first terminal connecting each of the at least one transmit driver to each of the at least one transducer element.

In some embodiments, the array is organized into rows and columns. The method also includes electronically selecting a plurality of transducer elements in the column to define a column of transducer elements.

In some embodiments, the plurality of delays of the transducer elements in the first column are independent of the plurality of delays of the transducer elements in the second column, and the plurality of delays of the transducer elements in the first row are independent of the plurality of delays of the pMUT transducer elements in the second row.

In some embodiments, the transducer elements on a column have different delays.

In some embodiments, the method further comprises performing 3D imaging by: the method includes applying a plurality of delays in an azimuth direction to a transmit set having a fixed steering angle in an elevation direction (the steering angle being controlled by the plurality of delays applied to transducer elements on the column), and repeating the sequence at different steering angles in an elevation plane, and reconstructing an image using echoes received from the transducers.

In some embodiments, the method further comprises performing volumetric imaging by: focusing on the azimuth plane by varying the multiple delays along the azimuth and also focusing or steering the beam in the elevation plane by varying the multiple delays of the transducers on the column.

In some embodiments, the method further comprises selecting the bias voltage from the group consisting of a ground voltage, a negative voltage, and a positive voltage.

Incorporated by reference

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. Rathod, vivek T. A Review of Electric Impedance Matching Techniques for Piezoelectric Sensors in 2019, actuators, and Transducers, lingvall, F. Time-domain Reconstruction Methods for Ultrasonic Array Imaging in 2004: A Statistical Approach.

Brief Description of Drawings

A better understanding of the features and advantages of the present subject matter will be obtained by reference to the following detailed description that sets forth illustrative embodiments, and the accompanying drawings.

Fig. 1 shows an exemplary schematic of an ultrasound system herein comprising a transducer having a pMUT array for transmitting and receiving ultrasound beams, electronics for controlling the pMUT array, other computing, control and communication electronics, a display unit and a recording unit, wherein the pMUT array is directed towards a target to be imaged.

Fig. 2 shows an exemplary schematic diagram of an ultrasound transducer.

Fig. 3A shows an exemplary schematic of a piezoelectric micromachined transducer (pMUT) element having 2 conductors.

FIG. 3B shows an exemplary schematic of a pMUT element including two subelements each having 2 or more electrodes.

Fig. 3C shows an exemplary schematic of a pMUT element with 2 subelements, each subelement having 2 electrodes, with a first electrode of a first subelement connected to one of the electrodes of a second subelement and a second electrode of the first element connected to the remaining electrode of the second subelement.

Fig. 4 shows an exemplary diagram of a pMUT array of the ultrasound transducer system herein.

Fig. 5 shows an exemplary cross section of a piezoelectric element of a pMUT array herein.

Fig. 6 shows dipole orientations in the piezoelectric element herein in an unpolarized state and during and after polarization.

Fig. 7 shows an exemplary connection of the piezoelectric element herein with a Low Noise Amplifier (LNA) in a symbolically connected arrangement during a receive mode.

Fig. 8A illustrates an exemplary embodiment of a 2D array of pmuts with one common ground or bias electrode for an electrically tunable line transducer in which the lines may be in either a vertical or horizontal direction and the size of the lines (e.g., the number of pMUT elements in the lines) may be electrically programmable.

Fig. 8B illustrates an exemplary embodiment of a 2D array of PMUTs with connections to bias voltages and/or active drive terminals shown.

Fig. 9A shows an exemplary schematic of 2 pMUT elements interconnected with an ASIC containing transmit and receive drivers and other functions.

Fig. 9B shows an exemplary schematic of the ASIC of fig. 9A, wherein a column of electronics is directly interfaced with a column of PMUTs to form a composite larger transducer element.

Fig. 10A and 10B illustrate exemplary schematic diagrams of an ultrasound transducer focused in the elevation direction disclosed herein.

Fig. 11 shows an exemplary schematic of an ultrasound transducer with transducer elements organized in M rows and N columns, the transducer comprising three strips of rows and/or columns, each strip being selectable for separate driving, and wherein the columns in each strip share the same driving by the transmit driver.

Fig. 12 shows an exemplary schematic of a plurality of scan lines that make up an ultrasound image frame.

Fig. 13 shows an exemplary schematic diagram of obtaining the scan line of fig. 12.

Fig. 14 shows an exemplary schematic diagram for obtaining elevation focus using delays applied to different stripes.

Fig. 15A shows an exemplary schematic diagram of a delay circuit having a plurality of flip-flops herein.

Fig. 15B shows an exemplary schematic diagram of the delay circuit herein.

Fig. 16 shows an exemplary schematic of transducer elements and their delays, which may be electronically programmed and may be substantially similar for more than one column of transducer elements.

Fig. 17 shows an exemplary schematic of the transmit drive pulse with delays for a column of transducer elements, the delays having symmetry around a central element.

Fig. 18 shows an exemplary schematic diagram of a transmit drive pulse with delays for transducer elements of different columns.

Fig. 19 shows an exemplary schematic of generating different delays using an internal counter signal.

Fig. 20 shows an exemplary schematic of a pulser having two digital inputs that generates an output as a transmit drive pulse.

Fig. 21 shows the elevation beam pattern of a simulated 24x128 matrix array with 0 ° lateral steering (left) and 45 ° lateral steering.

Fig. 22 shows a sparse Tx aperture that allows transmit elevation focusing with a 24x128 2d array.

Fig. 23 shows a schematic diagram of a piezoelectric element array capable of performing two-dimensional and three-dimensional imaging according to an embodiment of the present disclosure.

Fig. 24 shows a schematic diagram of an imaging system according to an embodiment of the present disclosure.

Fig. 25 illustrates an embodiment of a piezoelectric element coupled to a circuit element according to an embodiment of the present disclosure.

Fig. 26 illustrates a circuit for controlling a plurality of piezoelectric elements according to an embodiment of the present disclosure.

Fig. 27 illustrates a transmit drive signal waveform according to an embodiment of the present disclosure.

Fig. 28 illustrates a transmit drive signal waveform according to an embodiment of the present disclosure.

Fig. 29 illustrates a transmit drive signal waveform according to an embodiment of the present disclosure.

Fig. 30 illustrates input/output signals of various circuits in an imaging assembly according to an embodiment of the present disclosure.

Fig. 31A shows a graph of the amplitude of a transmitted pressure wave in the frequency domain, according to an embodiment of the present disclosure.

Fig. 31B illustrates a window of an apodization process (apodization process) according to an embodiment of the present disclosure.

Fig. 32 shows a schematic diagram of an imaging assembly according to an embodiment of the present disclosure.

Fig. 33A shows a circuit containing a piezoelectric element, which may be part of an array of piezoelectric elements.

Fig. 33B shows a modification to the circuit of fig. 33A, in which an inductor is connected in series between a piezoelectric element and an X bias node.

Fig. 33C illustrates a technique that uses an inductor between the transmit driver and the transducer it drives.

Fig. 33D shows one way to place the inductor to its ground (or V _{Bias of} ) And actual ground (or V _{Bias of} ) Is provided.

Fig. 34 shows a column of N piezoelectric element circuits of the type shown in fig. 33B connected to a common inductor placed in series between the piezoelectric elements (logically selected and connected in parallel with each other) and the X bias terminal.

Fig. 35 shows a plurality of columns of piezoelectric element circuits of the type shown in fig. 33A, which do not have an inductor connected between the piezoelectric element and the X bias terminal.

Fig. 36A shows an embodiment with multiple columns connected to a common X bias line.

Fig. 36B shows an embodiment in which a plurality of piezoelectric elements are arranged per column. A switch connected in series with the piezoelectric elements may be used to logically select each piezoelectric element. The inductor can be bypassed by a switch if desired.

Fig. 37 shows an implementation of an inductor consisting of a set of switchable and electronically selectable inductors.

Detailed Description

Ultrasound imaging has traditionally used bulk piezoelectric films as transducers. However, these tend to be expensive to use and also require high voltages, typically in the range of 100 to 200V to operate. Recently, transducers capable of mass production on silicon wafers using piezoelectric films dispensed or sputtered on silicon wafer substrates have become available. These transducers can integrate the system with a more compact or smaller form factor (form factor) and operate at lower power requirements and cost than legacy systems, and thus have significant advantages. Additionally, other transducer technologies (such as cmuts) have emerged that can be fabricated on silicon wafers with significant manufacturing cost advantages. However, these transducers (and legacy transducers) may present significant capacitive loading to the transmit driver. For applications requiring significant pressure output, adjusting the circuit impedance to achieve maximum power transfer is employed. It is well known that power transfer is maximized when the impedance of the driver is the complex conjugate of the load. The prior art shows that the use of an inductor between the driver and the load helps to increase the pressure output. However, this technique is not easily implemented for integrated portable applications or use cases due to size and parasitic impedance issues. A new technique will be shown to achieve the required integration at low cost and to achieve the required pressure output. The technique is applicable to pmuts and other transducers with significant capacitive loading, such as older bulk piezoelectrics and cmuts (capacitive micromachined ultrasonic transducers). Furthermore, the goal would be to achieve this in a way that enables excellent capabilities through the use of a 2D array of transducers and related circuitry housed in or with an ASIC. This enables the generation of 3D images and electronic focusing in azimuth and elevation directions. This capability has not been successfully implemented in hand-held ultrasound imaging devices due to cost, power and size limitations in legacy systems.

Traditionally, 2D ultrasound images can be created by employing various algorithms. One example of this is to use the relative delay for driving signals along the columns of piezoelectric elements in the azimuth direction. By varying the electronically programmable delays applied to the signals for different columns in the azimuth direction, the beam can be electronically focused in the azimuth direction. Focusing in a direction orthogonal to the azimuth direction (e.g., the elevation direction), however, is typically achieved through the use of a mechanical lens. Mechanical lenses may allow only one focus at a time, so different elevation focus may require differently designed lenses. Furthermore, the fixed mechanical lens does not provide the focusing required for 3D ultrasound imaging.

In some embodiments, disclosed herein are systems and methods configured for implementing low cost, low power, portable high resolution ultrasound transducers configured for ultrasound imaging, and ultrasound imaging systems. Implementation of these low cost, high performance systems may rely on the use of pmuts that can be manufactured on semiconductor wafers in high volume and low cost similar to high volume semiconductor processes. In an exemplary embodiment, such pmuts are arranged in a 2D array, wherein each element in the array is connected to an electronic circuit, wherein the pMUT array and the circuit array are aligned together and integrated together on different wafers to form a tile, wherein each piezoelectric element is connected to a control circuit element, wherein each piezoelectric element may have 2 terminals, as shown in fig. 3. These pmuts can also exhibit high bandwidths, making these transducers suitable for broadband imaging unlike prior art piezoelectric transducers. Additionally, existing transducers that utilize mechanical lenses for elevation focusing may also suffer from attenuation losses in the lenses, thereby degrading image quality. For the exemplary synthetic lenses herein, no mechanical lenses are required. Sometimes, a slightly curved deep focus weak lens may be used, or alternatively, a flat thin impedance matching layer may be used on top of the transducer. This can greatly improve attenuation losses.

The disclosed ultrasound transducer may be a capacitive micromachined ultrasound transducer (cMUT) device. Such a transducer may comprise a large array of cMUT elements. The cMUT array may provide a larger bandwidth than other transducer technologies, and may easily achieve high frequency operation.

The use of inductors using fixed mechanical lenses is disclosed. Furthermore, the imaging system disclosed herein also uses an electronic lens, which advantageously eliminates the need to construct a mechanical lens with a fixed focal length. Furthermore, the electronic lenses disclosed herein allow great flexibility in being able to vary the focal length in the elevation plane, and allow dynamic focusing as a function of depth.

In some embodiments, the transducer is a capacitive micromachined ultrasonic transducer (cMUT) device or a bulk piezoelectric transducer.

In some embodiments, the transducer elements on a column have different delays.

In some embodiments, the voltage drive level is further controlled using pulse width modulation of the transmit pulser waveform.

In some embodiments, the transducers are configured to provide electronic control of elevation focusing in the elevation direction along the column.

In some embodiments, the transducer elements along the columns are driven by multi-level pulses.

In some embodiments, the delay may be the sum of a coarse delay and a fine delay.

In some embodiments, 2N receive channels are used to address N columns.

In some embodiments, the ultrasound transducer is a pMUT device.

In some embodiments, the ultrasound imaging system includes multiple columns.

In some embodiments, the delay profile including delays from one or more transducer elements having a common column index is symmetrical.

In some embodiments, the delay is the sum of a coarse delay and a fine delay.

In one aspect, a method for increasing the pressure of ultrasonic waves emitted by a transducer comprising at least one transducer element is disclosed. The method includes placing at least one transducer element in a transmit mode using at least one transmit driver connected to the at least one transducer element. Each transducer element has a first terminal and a second terminal. The method further comprises the steps of: for at least one inductor, a first terminal of each of the at least one inductor is connected to a second terminal of each transducer element. The second terminal of the at least one inductor is connected to a bias voltage. The at least one inductor is not integrated with the transducer element. The transducer further includes each first terminal connecting each of the at least one transmit driver to each of the at least one transducer element.

In some embodiments, the transducer elements on a column have different delays.

Certain definitions

Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter pertains.

As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Any reference herein to "or" is intended to include "and/or" unless otherwise indicated.

As used herein, the term "about" refers to about 10%, 5%, or 1% of the amount, including increments therein, that are closer.

In some embodiments, the imagers (interchangeably herein "transducers") herein may be used to perform, but are not limited to performing: 1D imaging, also known as A-Scan;2D imaging, also known as B-scan; 1.5D imaging; 1.75D imaging; 3D and doppler imaging. Further, the imagers herein may be switched to various imaging modes that are preprogrammed. Furthermore, a biplane imaging mode may be achieved using the transducers herein.

In some embodiments, the transducer elements (e.g., pMUT elements, cMUT elements) herein are interchangeable with transceiver elements. In particular, pMUT elements herein are interchangeable with piezoelectric elements (piezoelectric elements) and piezoelectric elements (piezo elements). In some embodiments, the transducer elements herein may include one or more of the following: a substrate; a membrane suspended on the substrate; a bottom electrode disposed on the membrane; a piezoelectric layer disposed on the bottom electrode; and one or more top electrodes disposed on the piezoelectric layer.

Fig. 1 illustrates an exemplary embodiment of an ultrasound imaging system 100 as disclosed herein. In this embodiment, the image system comprises a portable device 101, the device 101 having a display unit 112, a data recording unit 114, the data recording unit 114 being connectable to a network 120 and an external database 122, such as an electronic health record, through a communication interface. Such connection to an external data source may facilitate medical billing, data exchange, querying, or other medical-related information communication. In this embodiment, the system 100 includes an ultrasound imager probe (probe) 126 (interchangeably herein "probe") and the probe 126 includes an ultrasound imager assembly (interchangeably herein "tile assembly") 108, wherein the ultrasound tile has one or more arrays of pmuts 102 fabricated on a substrate. The array of pmuts 102 is configured to transmit and receive ultrasound waveforms under an electronic control unit, such as an Application Specific Integrated Circuit (ASIC) 106 located on an imager, and another control unit 110.

In this particular embodiment, at least a portion of the display unit 112 and/or the electronic communication control unit 110 may be located on the component 108. In some embodiments, a portion of the display unit 112 or control unit 110 may be external to the imager, but connected to the ultrasound imager assembly 108 and its internal components using a communication interface 124, which communication interface 124 may be a wired communication interface and/or a wireless communication interface. For wired connections, many data exchange protocols may be used, such as USB2, lightning, and other protocols. Similarly, for wireless communications, commonly used protocols may be used, such as IEEE 802.11 (Wi-Fi) or other wireless communication protocols. Similarly, the data recording unit 114 may also be external to the sonde and may also communicate with the sonde 126 using a wireless or wired communication interface. In some embodiments, the display 112 may have an input device, such as a touch screen, a user-friendly interface, such as a Graphical User Interface (GUI), to simplify user interaction.

In the same embodiment, pMUT array 102 is coupled to an Application Specific Integrated Circuit (ASIC) 106 located on another substrate and in close proximity to pMUT array 102. The array may also be coupled to an impedance-reducing and/or impedance-matching material 104, which material 104 may be placed on top of the pMUT array. In some embodiments, the imager 126 includes a rechargeable power supply 127 and/or a connection interface 128 to an external power supply, such as a USB interface. In some embodiments, the imager 126 includes an input interface 129 for the ECG signal for synchronizing the scan to the ECG pulse. In some embodiments, the imager 126 has an inertial sensor 130 to assist in user guidance.

Conventional transducer arrays use piezoelectric materials, such as lead zirconate titanate (PZT), formed by dicing blocks of bulk PZT to form individual piezoelectric elements. These tend to be expensive. In contrast, the pMUT arrays disclosed herein are disposed on a substrate (e.g., wafer). The wafer may be of various shapes and/or sizes. As an example, the wafers herein may be wafers of various sizes and shapes used in semiconductor processes for building integrated circuits. Such wafers can be mass-produced at low cost. Exemplary wafer sizes are: diameters 6, 8 and 12 inches.

In some embodiments, many pMUT arrays can be mass manufactured at low cost. Furthermore, the integrated circuit may also be designed with dimensions such that the connections required for communication with the pMUT are aligned with each other and the pMUT array (102 of fig. 1) may be closely connected to a matching integrated circuit (106), typically vertically below or near the array by a distance, for example, about 25 μm to 100 μm. In some embodiments, the combination of 102, 104, and 106 is referred to as an imaging assembly 108 or block, as shown in FIG. 1. For example, one exemplary embodiment of the assembly 108 may have 1024 pMUT elements connected to a matching ASIC, with an appropriate number of transmit and receive functions for 1024 piezoelectric elements. The array size is not limited to 1024. It may be smaller or larger. Larger size pMUT elements may also be achieved by using multiple pMUT arrays 102 and multiple matching ASICs 106 and assembling them adjacent to each other and covering them with an appropriate amount of impedance matching material 104. Alternatively, a single array may have a large number of pMUT elements arranged in a rectangular array or other shape, with the number of pMUT elements ranging from less than 1000 to 10000. The pMUT array and the plurality of pMUT elements may be connected to a matched ASIC.

Arrow 114 shows the ultrasound transmit beam from the imager assembly 108 aiming at the body portion 116 and imaging the target 118. The transmit beam is reflected by the imaged object and enters the imager assembly 108 as indicated by arrow 114. In addition to the ASIC 106, the imaging system 100 may include other electronic control, communication, and computing circuitry 110. It should be appreciated that the ultrasound imager 108 may be a stand-alone unit as shown in fig. 1, or it may include physically separate but electrically or wirelessly connected elements, such as a portion of the electronic control unit 110. This example is shown in fig. 2.

Fig. 2 shows a schematic diagram of an imager 126 according to an embodiment of the disclosure. As depicted in fig. 2, the imager 126 may include: a transceiver array 210a for transmitting and receiving pressure waves; a coating 212a that acts as a lens for manipulating the direction of propagation of the pressure wave and/or focusing the pressure wave, and also acts as an impedance interface between the transceiver array and the human body; lens 212a, which may also cause attenuation of signals that leave the transducer and also enter the transducer, is therefore also desirably kept to a minimum; when elevation control is electronic, such a lens may not be required and may be replaced with only a thin protective impedance matching layer where losses are only minimal; a control unit 202a, such as an ASIC chip (or simply, ASIC), is used to control the transceiver array 210a and is coupled to the transducer array 210a by bumps. The combination of the transceiver array and the ASIC connected thereto constitutes a block. Additional components may include one or more Field Programmable Gate Arrays (FPGAs) 214a for controlling components of the imager 126, circuitry 215a for processing/conditioning signals, such as an Analog Front End (AFE); and an acoustic absorption layer 203a for absorbing waves generated by the transducer array 210a and propagating toward the electrical circuit 215 a. In certain embodiments, the absorber layer is located behind the ASIC (relative to the transducer in front of the ASIC), as depicted in fig. 2; in certain embodiments, the absorber layer is located between the transducer and the ASIC; in certain embodiments, these absorber layers are not required. Additional components may include a communication unit 208a for communicating data with external devices, such as device 101, through one or more ports 216 a; a memory 218a for storing data; a battery 206a for providing a more portable power supply to the components of the imager; and optionally a display 217a for displaying a user interface and ultrasound-derived images. During operation, a user may bring the surface of pMUT 102 covered by interface material 104 into contact with a body part region on which ultrasound waves are emitted toward the target 118 being imaged. The imager receives the reflected ultrasound beam from the imaging target and processes it or transmits it to an external processor for image processing and/or reconstruction and then transmits to the portable device 101 for displaying the image. Other data may also be collected, calculated, derived, and displayed to the user on a display.

When using an imager, for example, to image a human or animal body part, the emitted ultrasound waveform is directed to the target. Contact with the body is typically achieved by holding the imager in close proximity to the body after the gel is applied to the body and the imager is placed on the gel to allow the upper interface (superior interface) of the emitted ultrasound waves to enter the body and also to allow the reflected ultrasound waveforms from the target to reenter the imager, wherein the reflected signals are used to create an image of the body part and the results displayed on the screen, including charts, graphs, statistics of the image with or without the body part displayed in various formats.

It should be noted that the sonde 126 may be configured with portions that are physically separate but connected by a cable or wireless communication connection. As an example, in this particular embodiment, the pMUT assembly and ASIC, as well as some control and communication related electronics, may reside in a unit commonly referred to as a sonde. The portion of the device or probe that contacts the body part contains the pMUT assembly.

Fig. 3A shows a cross-section of a schematic diagram of a conventional piezoelectric element 214. In this embodiment the piezoelectric element has 2 electrodes, a first electrode 216 connected to the signal conductor 215 and a second electrode 218 connected to the second conductor 217, the second conductor 217 being typically connectable to ground or other DC potential.

Piezoelectric elements have been used for ultrasound medical imaging for decades. However, the piezoelectric element may be thick, e.g., near about 100 μm, and may typically require +100V to-100V Alternating Current (AC) to drive through it to generate ultrasonic pressure waves of sufficient intensity to achieve medical imaging. The frequency of the AC drive signal may be near the resonant frequency of the piezoelectric structure and may be above 1MHz for medical imaging applications.

In some embodiments, the power dissipated in driving the piezoelectric element is equal to C ² In proportion, where C is the capacitance of the piezoelectric element and V is the maximum voltage across the piezoelectric layer. When transmitting, the multiple piezoelectric elements may be driven together with slightly different delays to focus the beam or steer the beam. Simultaneous driving of many components can result in an increase in temperature on the component surface. It is highly desirable or required that the threshold temperature not be exceeded so as not to harm the object being imaged. Thus, the threshold temperature limits the number of elements that can be driven and the period of time that they can be driven.

Disclosed herein, in some embodiments, the piezoelectric element is much thinner, about 1 μm to 5 μm thick, compared to about 100 μm thickness of conventional bulk piezoelectric elements. Such a large thickness reduction may enable the piezoelectric element to use a lower voltage drive signal to maintain an electric field strength similar to that of conventional elements. For example, the piezoelectric elements disclosed herein may require a drive voltage ranging from about 5V to 20V peak-to-peak.

The capacitance of the piezoelectric element may also be increased by reducing the thickness of some piezoelectric materials. Thus, as an example, when driving a film having a thickness of 1/10 of the original, the capacitance may be increased by a factor of 10 for a thinner piezoelectric material and the power consumption may be 1/10 of the original when the driving voltage is reduced from 100V to 10V. This reduction in power consumption may also reduce heat generation and temperature rise in the imaging detector. Thus, using a lower drive voltage, the temperature of the pMUT surface can be reduced.

In some embodiments, for a given temperature, when using a low voltage pMUT, more pMUT elements may be driven to illuminate a larger area. This may allow for faster scanning of the target, particularly if multiple shots are required to scan the entire target to form an image. In general, the target area may be scanned with multiple shots using different steering angles and the image data combined to obtain a higher quality image.

It may also be desirable to image at a high frame rate. The frame rate measures the number of times a target is imaged per minute. When tissue motion is involved, it is desirable to image at a high frame rate to observe the movement of the target without blurring the image. In some embodiments, the ability to drive more piezoelectric elements enables more coverage of the transducer aperture per transmission, minimizing the number of transmissions required to cover the entire aperture, thereby increasing the frame rate.

In some embodiments, image quality may be improved by combining several frames of images into one composite low noise frame. However, this reduces the frame rate. When using a low power pMUT, where the frame rate is higher than that of a conventional piezoelectric membrane, this averaging technique can be used in the event that pMUT temperature rises to some extent, since the low voltage pMUT has a lower power, thus achieving an inherently higher initial frame rate. In some embodiments, a synthetic aperture method of ultrasound imaging may be used to allow for compositing of images.

In some embodiments, the ability to drive more piezoelectric elements at a time improves the signal-to-noise ratio (SNR) and achieves better quality of the reconstructed image.

Further, as depicted in fig. 1, ASIC 106 is coupled to pMUT 102. The ASIC may include a Low Noise Amplifier (LNA). The pMUT is connected to the LNA through a switch in the receive mode. The LNA converts the charge in pMUT generated by the reflected ultrasound beam exerting pressure on pMUT into an amplified voltage signal with low noise. The signal-to-noise ratio of the received signal may be one of the key factors in determining the quality of the reconstructed image. Therefore, it is desirable to reduce the inherent noise of the LNA itself. This can be achieved by increasing the transconductance of the LNA input stage. This can be achieved by using a larger current in the input stage, for example. Larger currents may result in increased power consumption and heat. However, where a low voltage pMUT is used and is in close proximity to the ASIC, the power saved by the low voltage pMUT may be used to reduce noise in the LNA for a given acceptable overall temperature rise when compared to a transducer operating at high voltage.

Fig. 3B shows a schematic diagram of a pMUT element 220 disclosed herein. It consists of 2 sub-elements 220a and 220 b. In this embodiment, the sub-element 220a has a piezoelectric layer 221, wherein a first electrode 223 is connected to a first conductor 222 and a second electrode 224 is connected to a second conductor 226. The sub-element 220b has a first electrode 228 connected to a first conductor 229 and a second electrode 225 connected to a second conductor 227. Typically, the second conductors of the two subelements are connected together and to a bias voltage.

FIG. 3C is a schematic diagram of a pMUT element 230 having 2 subelements 230a, 230 b. In some embodiments, each pMUT element includes one or more subelements. In this embodiment, each subelement has a piezoelectric layer 231 with a first electrode 233a connected to a first conductor 232a and a second electrode 234a connected to a second conductor 235a, with the first conductors of all subelements being connected together by a connector 2220 and the second conductors of all subelements being connectors connected together by a connector 2260. The second subelement 230b has a piezoelectric layer 231 in which a first electrode 233b is connected to a first conductor 232b and a second electrode 234b is connected to a second conductor 235b.

In some embodiments, the element may be composed of more than 2 sub-elements, wherein the first electrodes of all sub-elements are connected together, typically to a drive signal, and the second electrodes of all sub-elements are also connected together, typically to a bias voltage.

Fig. 4 shows a substrate 238 with a plurality of piezoelectric micromachined ultrasonic transducer (pMUT) array elements 239 disposed on the substrate 238. In this embodiment, one or more array elements form a transceiver array 240, and more than one transceiver array is included on a substrate 238.

Fig. 5 shows a cross section of an exemplary embodiment of the piezoelectric element 247. In this embodiment, element 247 has a thin piezoelectric film 241 disposed on a substrate 252. The piezoelectric film has a first electrode 244 connected to a signal conductor 246. The electrode is typically deposited on a substrate on which SiO2 is grown. A layer of TiO2 is deposited and then a layer of platinum is deposited, on which PZT is sputtered or PZT sol gel is applied to develop a thin layer of PZT into the piezoelectric film 241. The piezoelectric film 241 and the first metal electrode are patterned into a desired shape by etching. The signal conductor 246 is connected to the first electrode. The second electrode 240 is grown over the thin film 241 and connected to the second conductor 250. The third electrode 242 is also grown adjacent to, but electrically isolated from, the second electrode. The third conductor 248 is connected to the third electrode. The actual layout of the electrodes shown may vary from square to rectangular, oval, etc. adjacent electrodes or ring electrodes, one surrounding the other. The piezoelectric film may have different shapes and may be present in certain portions over the substrate and cavity.

Due to the asymmetry of the PZT crystal structure, an electrical polarity is formed, creating an electrical dipole. In the macroscopic crystal structure, the dipoles may exist in random orientations by default, for example as shown on the left side of fig. 6. When the material is subjected to mechanical stress, each dipole can rotate from its original orientation in a direction that minimizes the total electrical and mechanical energy stored in the dipole. If all dipoles are initially randomly oriented (i.e., the net polarization is zero), their rotation may not significantly alter the macroscopic net polarization of the material, and thus exhibit negligible piezoelectric effect. It is therefore important to create an initial state in the material such that most dipoles are more or less oriented in the same direction. This initial state may be imparted to the material by polarizing the material. The direction along which the dipoles align is called the polarization direction. The dipole orientation during and after polarization is shown in fig. 6 (middle and right panels).

Thus, the piezoelectric film may need to be polarized prior to use. This can be achieved when the film is sputtered in the field. This can also be accomplished after manufacture by applying a high voltage to the film, typically at an elevated temperature (e.g., 175 ℃) for a period of time (e.g., 1-2 minutes or more). In the piezoelectric element of fig. 3, pMUT may be constructed with 2 terminals and a high voltage may be applied, for example, between 216 and 218. For a 1 μm thick piezoelectric film, the high voltage may be about 15V. Such voltages are sufficient for polarization.

Pmuts of the prior art or other piezoelectric elements from bulk PZT typically have two electrodes. As disclosed herein, the piezoelectric element may have 2 (in fig. 3) or more electrodes, as shown in fig. 5. In fig. 5, the first conductor during polarization may be connected to ground potential, while the second conductor is connected to a negative potential, e.g. -15V for a 1 μm thick PZT film, and the third electrode is connected to +15v for a period of time at high temperature. This may create two polarization directions on the PZT film that are opposite for the piezoelectric film between the first conductor and the second conductor compared to the piezoelectric film between the first conductor and the third conductor. After polarization is completed, the second and third conductors may be connected to ground or bias voltage during transmit or receive operations, while the first conductor is connected to an ASIC to be driven by the transmit driver during transmit operations or to the LNA through a switch during receive operations. The second conductor and the third conductor may also be connected to a non-zero DC bias, wherein the bias values may be different.

The piezoelectric element in the exemplary embodiment utilizes lateral strain, and utilizes PZT lateral strain constant d31, i.e., piezoelectric coefficient, to generate movement of the membrane or to convert movement of the membrane into electric charge. The PZT element of fig. 5 having orthogonal polarization directions of the film amplifies the movement of the film for a given drive in the firing operation, as compared to the structure shown in fig. 3A where the film has only one polarization direction. Thus, the emission sensitivity can be improved, allowing for greater movement of the membrane under the emission drive applied per volt.

In the receive mode, the orthogonal polarization direction may produce more charge to be sensed by the LNA. The connection of the LNA is symbolically shown in fig. 7. For simplicity, not all elements in the path connecting the piezoelectric element to the LNA are shown. In some embodiments, the piezoelectric element 260 has a first electrode 274 connected to a switch in series with the LNA 268, the first electrode and the switch being connected by a conductor 262. The second electrode of 260 is 266 and may be connected to a DC bias including 0V (ground). 270 represents the reflected ultrasonic beam striking pMUT element 260 and creating an electrical charge on electrodes 266, 274. It is noted that the LNA may be designed to operate in either voltage or charge mode. pmuts can tend to have large capacitances, and for a given amount of charge, if voltage sensing is used, pmuts will produce lower voltages across the transducer than much smaller PZT bulk elements, with the voltage on the transducer being amplified. The output noise is larger due to the smaller voltage at the LNA input. Charge amplification may provide a better signal-to-noise ratio at the output of the LNA than voltage mode operation due to the high capacitance of the pMUT element, especially when pMUT produces more charge output for a given input pressure in the receive mode. This is illustrated in fig. 7, where any charge received by Ct is transferred through a much smaller capacitor Cf, producing a greater voltage at the output of LNA 272. These LNAs are also designed so that they can be powered on or off quickly.

Conventional 2D imaging is accomplished using columns of elements arranged in a rectangular shape. Alternatively, 2D imaging may be achieved by taking many smaller elements arranged in columns. Individual array elements may be combined into a single larger 1D array element to form a column. This is accomplished by hard-wiring these individual elements to create a larger element with one signal conductor and a common ground conductor. Transmit driving, receive sensing and control are implemented for this one combination and larger two-lead pMUT.

Fig. 8A shows a schematic diagram of an exemplary embodiment of an ultrasound imaging array 300 of a transducer herein. For illustration, the array shows 9 pMUT elements arranged in 3 rows and 3 columns or 3 x 3. It should be appreciated that in practice, the array size may be of various sizes, larger or smaller as desired. Non-limiting examples of sizes include: 32×32, 32×64, 32×194, 12×128, 24×128, 32×128, 64×128, 64×32, 64×194 (column×row or row×column).

In fig. 8B, the conductor of each piezoelectric element is connected to an electrode and is named Oxy, where x ranges from 1 to 3 and y ranges from 1 to 3. The first conductor of each piezoelectric element is connected to a first electrode and is designated O11. Furthermore, all elements for an electronically configurable imager have O leads connected to corresponding electronics located on another wafer. The second electrode of each element, called X, is connected to the other X electrode for the other element by a conductor 302. Conductor O is a signal conductor and X is a ground or bias line. In this embodiment shown in fig. 8B, the O electrode is connected to the ASIC immediately adjacent to the substrate on which pMUT is disposed. In the exemplary case where there is an array of 32×32 pmuts, there are 1024 piezoelectric elements. There may be 1024 "O" wire connections to the ASIC, typically under the pMUT die. Each of these 1024O-lines is connected to the transmit driver during transmit operation and to the input of the LNA during receive operation, where the transmit driver enters a high impedance state in receive mode.

Fig. 9A is a schematic representation of 2 transducer elements interconnected with an ASIC 500. In some embodiments, the 2 transducer elements 502 are on one substrate 504 connected to an ASIC that contains the transmit and receive and other functions on another substrate 512. The input of LNA 516 is connected through switch 514 to lead 510, which lead 510 connects it to the signal conductor O-lead of the transducer. In some embodiments, the bias conductor 506 is connected into the ASIC and then out of the ASIC to connect to ground or other bias voltage. These are the X-leads of the transducer and can be connected together with other X-leads in the transducer and ASIC. As indicated at 520, the transmit driver 518 may be controlled by communication external to the ASIC on the substrate 512. It may also be connected to a switch 514 that is shown connected when in the transmit mode. The output of the LNA and the input of the transmit driver as shown in fig. 9A may require 2 different leads. By using a multiplexer switch similar to 514, one lead may be used. In some embodiments, the connection to the LNA output may be provided to external electronics in a receive mode, and the input to the transmit driver may be provided in a transmit mode.

Fig. 9B shows a schematic representation of some of the functions of a column of electronics in an ASIC. The column electronics can be directly connected to a column of pMUT interfaces to form a composite larger wire element. It should be understood that the ASIC may contain circuitry for other columns or rows and include other support circuitry not shown. It should also be appreciated that the actual functions desired may be implemented with different circuit topologies as would be apparent to one of ordinary skill in the art. The representation shown is only intended to illustrate the idea itself.

Fig. 9B shows an exemplary schematic of a column of ASIC 600. In certain embodiments, the conductors 608 are connected to corresponding signal conductors O31 of elements in the pMUT arrays of fig. 8A-8B. Similarly, O21 of FIGS. 8A-8B is connected to 628 of FIG. 9B. The transmit driver 606 may be connected to the conductor 608 in fig. 9B. The driver 606 may have a switch 602 connected to its input and to a lead 616 (the signal conductor of the line element), the lead 616 being connected to the input of the other transmit drivers in the column through the switch on the column. The switches may be controlled by 624, and 624 may determine which switches to turn on via communication with an external controller. The signal conductor 616 may also be connected to electronics implementing a transmit beamformer. The O conductor 608 may also be connected to the switch 604; the other side of switch 604 may be connected to a similar switch (e.g., 622) in the column. Line 614 may also be connected to an input of a Low Noise Amplifier (LNA) 618. Only one LNA may be required per line element (or column). The LNA may be activated by the control unit 624 in the receive mode, which also turns on the switch (e.g., 604) while turning off the other switches (e.g., 602). This may connect (via connection 608) the signal electrode of pMUT to an LNA, which may amplify the received signal and convert it to a voltage output 620 with low additive noise. Note that in the receive mode, the controller may also cause the transmit drivers to enter a disabled mode in which their output impedance becomes very high so as not to interfere with the received signal. In transmit mode, when the piezoelectric element should not transmit, switch 610 may be turned on and switches 602 and 604 turned off to ensure a net zero volt drive on the pMUT signal and bias electrode of the element that should not transmit when in transmit mode (net zero volt drive). The X-rays are also connected to the ASIC. Note that in fig. 8A to 8B, only 1 bias electrode X is shown. There may be multiple bias electrodes.

For simplicity, fig. 9B shows only the connection to one of the 2 bias conductors (X in fig. 8).

In some embodiments, conductor 612 in fig. 9B may be connected to X,302 in fig. 8. In some embodiments, the conductor 613 in fig. 9B may also be connected to X,302, but at a location closer to 613, and so on. Note that these additional interconnects 613 and 615 are not required, and at least one connector (612 or 613 or 615) is required.

Fig. 9B shows that 2 leads may be required for receive output 620 and transmit input 616. However, when a multiplexer is used, a single wire may be used for this purpose.

The line imagers herein may include a plurality of columns of piezoelectric elements, each column being connected to the controller by at least one signal and bias lead. The pulse of the appropriate frequency drives the wire. The other lines are driven by delayed versions of the pulse. The amount of delay of a line is such that it allows the transmitted composite beam to be steered at an angle or focused at a depth, an operation referred to as beamforming.

The line imagers of fig. 8A and 8B are electronically configurable. Using an example of a piezoelectric element array in which 24 elements are arranged in one direction and 64 elements are arranged in an orthogonal direction (azimuth direction for this example), a 64-line imager can be constructed in which each line is composed of up to 24 elements. However, the size of any line can be electronically adjusted between 0 and 24 elements, and any number up to 64 lines in azimuth can be activated.

In 2D or 3D imagers, it is desirable to image thin slices of the elevation plane as shown in fig. 10A and 10B. In this particular embodiment, the elevation direction is on the ya axis on the left panel. Elevation plane 1201 is in the ya-za plane. In the same embodiment, azimuth plane 1202 (also herein the scan plane) is orthogonal to the elevation plane. Referring to fig. 10B, a mechanical lens focuses the beam in the elevation plane, preventing the beam from deflecting to form a much thicker slice in the elevation plane and hitting other objects in the thicker elevation slice, where unwanted reflections become part of the received signal, adding signal clutter (signal cluttering) and degrading image quality.

If the beam propagates far beyond the expected slice thickness, it may hit targets outside the desired range, whose reflections will produce clutter in the reconstructed image. The mechanical lens formed on the transducer surface can focus the beam in the elevation plane to a fixed elevation slice thickness, as seen in fig. 10B, where the thickness is minimal at the elevation focus, as seen in fig. 10B, and is also marked as elevation plane focus on fig. 10A. Electronic focusing for 2D imaging will allow improved focusing in the elevation plane by dynamic receive focusing as a function of time. Here, the focal length in elevation varies as the beam propagates toward the target, producing a superior image. For 3D imaging, a fixed mechanical lens does not work because a particular elevation slice cannot be steered or swept through the desired volume. Thus, electronically controlled elevation focusing is desired.

In some embodiments, this is achieved by dividing the transducer into a plurality of different strips. Referring to fig. 11, in a particular embodiment, the transducers are organized into N columns, with each column having up to M rows of elements of the transceiver. The rows of elements may be divided into a strip a, a strip B and a strip C, the strip a comprising a first number of rows, wherein the strip a has up to N columns, the strip B comprising a second number of rows in a central portion of the rows, wherein each row has up to N columns, and the strip C comprises a lower portion of the rows of up to N columns. The strips a, B and C may not overlap with adjacent strips. Alternatively, the strips may overlap with their adjacent strips by multiple rows and columns. In some embodiments, these strips together cover all N columns and M rows of transducer elements. In some embodiments, when all of these strips are electrically programmed, they together may cover only a portion of the mxn array of transducers.

In some embodiments, the top portion a is organized such that all elements in the portion are driven by the firing driver for the column in which the elements are located. In this embodiment, in transmit operation, N transmit drivers with unique delays driving N composite columns (each composite column may include elements from a row of stripe a or stripe B or stripe C) are used to focus the ultrasound beam in azimuth plane 1202. During the reception operation, the reflected signal incident in the portion a is beamformed to produce scan lines Al, A2, A3, and the like, as shown in fig. 12. Referring to FIG. 12, three bands of pMUT are labeled A, B and C. These strips include rows of pmuts in which the elements on a column are driven by a common transmit driver, with N drivers for N columns (i.e., a different driver for each of the N columns). The scanning lines Al, A2, and the like can be formed by using the emission and reception of the stripe a. The scanning lines Bl, B2, etc. are formed by the portion B, and the scanning lines Cl, C2, etc. are formed by the portion C. Now using scan data from 3 sections, this time another focusing in the elevation direction is performed with a similar technique using unique delays from the data of section a, section B and section C, which was used to previously focus the beam in the azimuth plane using delays along the column drivers. This process may be considered a dual stage beamformer where the first stage includes generating the scan lines of A, B, C and the second stage uses this data to form focus in the elevation plane. Focusing in elevation is achieved in the receiver by digitally applying delays. This technique allows focusing not only in the elevation plane, but also allows focusing to be dynamic. In this case, the focal length may be adjusted over time to allow elevation focusing to propagate with the ultrasound beam.

Although the process described in fig. 13 and 14 may require three transmissions and receptions, the first and second transmissions and receptions from portions a and C may be combined into one operation. In some embodiments, the emission from the top and bottom portions of the transducer may be performed simultaneously, with the delays on the top and bottom portions of the column being the same. The second transmission is from a central portion having a delay different from the delay used in the first and/or second transmissions.

In some embodiments, the top portion, the center portion, and/or the bottom portion may be divided into one or more sub-portions, each sub-portion including multiple rows for pulse transmission and signal reception. In some embodiments, each subsection may be used to form multiple scan lines in a manner similar to that disclosed herein.

In some embodiments, the array of transducer elements may be divided into more than 3 strips, e.g., 4, 5, 6, 7, etc. In some embodiments, the scan lines in each stripe may be performed sequentially or simultaneously. In some embodiments, in simultaneous transmission emission, scan lines from a stripe that is symmetrical to the center stripe are obtained. In some embodiments, the delays of elements in the same column are the same for portions that operate simultaneously.

Focusing may also be aided by further applying a lower amplitude voltage to a portion of the two outer portions of the transducer relative to the rest of the transducer.

In some embodiments, a unique programmable delay in the elevation direction is implemented for each element of all columns. All N columns may receive drive signals that are delayed relative to each other. Additional delays may be generated to add further delays along the column elements, where each element along the column may be differently delayed relative to its adjacent neighbors on the same column. An example of a delay profile is shown in fig. 16. The delays of all column elements in the elevation direction may be similar. In one embodiment, the delay is symmetrical, with a maximum at the central element for focusing in the elevation plane. The amount of delay difference between the outer element and the central element determines the focal length.

In some embodiments, the delay profile is shown in fig. 16, where the relative delay at the edge elements of the columns may be 0 rd or 0ns. For the elements on row 1 and R22, if symmetrical delays around the center element are desired, the delay relative to the delay at row 0 may be α ₁ * RD, and so on, as shown in fig. 16. Delay RD is programmable to alpha ₁ 、α ₂ Etc. Thus, a delay profile can be formed along the column, whereinThe delay may be a delay at the edge of the column. The relative delay profile may be the same for other column elements. In other embodiments, the delay profile may not be symmetrical about the central element and may be arbitrarily programmed. In some embodiments, the delay is in the range of 25ns to 1000 ns. In some embodiments, the delay is programmable, with different ranges of 10ns to 5000 ns. In some embodiments, the delay is in the range of 50ns to 500 ns.

In some embodiments, a process for obtaining scan lines using the systems and methods herein is shown in fig. 13. In some embodiments, the reflected signal is received by a transducer, the signal is converted to a voltage, and amplified and digitized by an analog-to-digital converter (ADC). These received signals are also referred to as RF signals. These RF signals may be delayed by τn (e.g., τ1, τ2, τ3, τ4.) and summed to form a scan line, such as Al, A2, etc., in fig. 12. In some embodiments, the signals are delayed and weighted by coefficients and then summed to form a scan line.

In some embodiments, focusing the beam in the receive direction utilizes one or more RF signals, e.g., S1, S2, etc., in the azimuth direction (Y), which are digitized output samples referred to as RF signals. In some embodiments, the RF samples are delayed, for example, with the delay profile along the Y-direction, and the resulting signals may be weighted and summed to form a scan line.

As shown in fig. 12, the scan lines A1, A2 and additional scan lines may be obtained using the portion a in successive transmit and receive events. In some embodiments, the image frame may include a number of scan lines, such as 100 or even more scan lines, to enable fine scanning of the imaged target area. A similar procedure can be used to obtain scan lines using part B and part C. The scan lines from sections a, B, and C are generated using a first level beamformer, where the beamformer generates the scan lines using an algorithm that, in the described embodiment, uses the signal delay and sum method described previously. Focusing in the elevation plane is then achieved using a synthetic aperture, second level beamformer, as shown in fig. 14. In some embodiments, these transmissions are focused at a single elevation angle (0 degrees, 10 degrees, 20 degrees, 30 degrees, etc.), thereby reducing out-of-plane clutter that is not in the elevation plane and obtaining improved images.

Referring to fig. 14, in a particular embodiment, the second stage focus/beamformer uses beam data (i.e., scan line data) from: a1, B1 and C1; a2, B2 and C2; a3, B3 and C3; etc., the data is delayed, weighted, and summed to form the final beam output, allowing elevation plane focusing. In this embodiment, X is the elevation axis.

Unlike mechanical lenses, as disclosed herein, with synthetic lenses, focal lengths can be electronically programmed into the beamformer. In some embodiments, the process may require multiple transmissions and receptions (e.g., 1 transmission and reception from N lines to form scan line A1) to form a scan line from any portion of the transducer (e.g., portion a, portion B, and portion C). In order to form a frame, R scan lines are required to scan the entire region to be imaged. In addition, in this case, 3 separate frames a, B, C are required. In some embodiments, it is desirable to have a high frame rate in the image. A frame may include many scan lines. However, if the number of transmissions and receptions can be reduced while the same number of scan lines can be formed, the frame rate will increase. In some embodiments, increased frame rate may be achieved by combining transmissions and receptions from two portions (e.g., a and C). Since these regions are symmetrical with respect to the central region, for example as shown in fig. 13, the delay required for region a and region C may be the same. By combining the two regions into one combined region to transmit and receive signals from, the frame rate can be increased by 150%. The center portion B may require a different delay than that used in the first transmission for the region a and the region C. In some embodiments, scan lines A1, B1, C1, etc. are formed along an azimuthal plane. The second beamforming operation may use data from the first level beamformer and focusing may be achieved in the elevation plane using similar techniques as shown in fig. 13 and 14. In some embodiments, the 2D scan may be done starting from one side of the strip (e.g., column N) and at the other end (e.g., column 1). Thus, frame a may be obtained by scanning beams A1, A2, AN … … in sequence. Next, following this sequence, frame B is obtained, which is a sequential frame in time of frame a, the target may have moved. To minimize the effects of motion artifacts, beamforming may be accomplished by interleaving scan lines of different frames (such as A1, B1, C1, A2, B2, C2, etc.). When a and C are combined so that transmission and reception can be completed together, the combined A, C area can be named D, and the scan line can be named D1, D2, or the like. Non-limiting exemplary scan sequences can be D1, B1, D2, B2, etc. This may help to minimize the sensitivity of movement in the imaged object.

In some embodiments, the number of rows used to form A, B, C is programmable. The number of rows may be adjusted according to the anatomy being imaged and may be set in the user interface using, for example, presets based on anatomy or patient information.

In some embodiments, the einzel lens provides dynamic focusing and dynamic aperture. For example, in the near field, the weights of a and C may be minimal and gradually increase with depth, resulting in a change in aperture.

In some embodiments, portions (e.g., portions a and C) are apodized during transmission and reception. Apodization can be achieved by Pulse Width Modulation (PWM) of the transmit (Tx) drive waveform. The non-apodized pulse drive has a nominal pulse width. When the pulse width is changed (e.g., reduced), the pressure output from pMUT may be reduced. In some embodiments, apodization is when the element tapers from the center to the edge of the transducer. This can reduce side lobes and create higher quality images. By applying apodization to the described process, signal leakage outside the elevation plane can be reduced.

In some embodiments, apodization can be achieved by using multi-level (e.g., 3 or 5 or 7 level) transmit drives. By selecting different levels of the drive signal, apodization can be created by applying a transmit drive signal that varies in amplitude, the amplitude of the transmit drive signal being lower for elements closer to the transducer edge than the center. In this example, all elements on the outer rows may have lower drive voltages than the center row, and some drive levels may be used to form a multi-level output through digital decoding and selection. An example of three-level decoding is shown in fig. 20.

In some embodiments, apodization is achieved by employing a piezoelectric element at the edge that is smaller than the piezoelectric element size at the center of the transducer aperture.

In an embodiment, the circuit employs a programmable delay in the elevation direction for all columns. All N columns may receive drive signals that are delayed relative to each other. Additional delays are generated to add further delays to the elements along the column, where each element along the column may be differently delayed relative to its adjacent neighbors on the same column. An example of a delay profile is shown in fig. 16. Thus, the array element ele _i,j The effective delay of (1) is the group column delay τ _j Then sum single line delay τ _i A kind of electronic device.

τ _i,j ＝τ _j +τ _i (1)

Wherein in one embodiment:

in the above equation, the focal point on the emission is at position (x, y, z), and for position x _j ,y _i The elements at that point calculate the delays independently. The variable c is the speed of sound in the hypothetical propagation medium. Note that in the case of perfect, inseparable focusing, the transducer element ele _i,j The delay of (2) is calculated as follows:

the separability of the delays in azimuth and elevation are assumed to be imperfect and the largest error in the delay profile will occur on the outer elements of the focus aperture. However, this separability assumption provides satisfactory results and ease of electronic implementation for the case of small steering angles and large f/#. The delays along all columns of elements of the elevation angle are similar. The delay profile may be symmetrical with the maximum delay at the center of focus in the elevation plane. The amount of delay determines the focal length. A shallow depth of focus requires a relatively long delay, e.g. on the order of hundreds of nanoseconds, while a deep depth of focus requires a shorter delay, e.g. on the order of a few nanoseconds. Another technique employs programmable delays in the elevation direction for all columns. All N columns may receive drive signals that are delayed relative to each other. Additional delays are generated to add further delays to the elements along the column, where the elements along the column may be differently delayed relative to their adjacent neighbors on the same column. Thus, an asymmetric delay with respect to the central element on the column can also be achieved.

In another embodiment, a programmable delay is employed in the elevation direction, where the elevation delay is the sum of a coarse linear delay and a fine arbitrary delay. Also, all N columns receive drive signals that are delayed relative to each other. An elevation delay is generated to increase further delays along the column of elements, wherein each element along the column is delayed by a coarse delay that may be linear between adjacent elements and a fine delay that may be linear or nonlinear between adjacent elements. The linear delays and fine delays along the column elements may vary from column to column. Thus, the array element ele _i,j Will be the group column delay τ _j Linear coarse line delay τ _{i, coarse} And a fine line delay tau _{i, thin} A kind of electronic device.

τ _i,j ＝τ _j +τ _{i, coarse} +τ _{i, thin} (5)

Wherein in a preferred embodiment:

τ _{i, j, coarse} ＝Δτy _i

In the above equation, the focal point on the emission is at position (x, y, z), and for position x _j ,y _i The elements at that point calculate the delays independently. The variable c is the speed of sound in the hypothetical propagation medium. In equation (6), parameter y _min Is calculated by projecting the focal spot (x, y, z) onto the 2D transducer plane and calculating the transducer row position of the minimum distance to the projected focal spot. The slope delta tau of the coarse delay can be calculated so that the fine delay can be used to give a good approximation of the perfect 2D delay.

It should be clear to a person skilled in the art that the above-described method for calculating the delay gives a better approximation to the 2D focus delay of equation (4) than the aforementioned X-Y separable delay. The improved delay computation comes at the cost of requiring a coarse delay clock, a fine delay clock, and more register bits to achieve different delays on a column-by-column basis. However, this approach is easier to implement in an integrated circuit than having a fine clock delay and a completely arbitrary delay in two dimensions of the individual element wirings. In another embodiment, a series of cascaded flip-flops arrive at the column clock from the Tx beamformer with an appropriate delay strobe (gate). The delay then propagates through the columns by a different clock whose frequency is programmable but synchronized with the Tx clock that generates the delays for the drivers of the various column drivers. For symmetrical delays around the central element on the column, the flip-flop chain that generated the delay stops at the central element of the column, with the delay profile symmetrical around the center, as described in fig. 17. The delay generated by the flip-flop is routed to the appropriate location so that the element of row 0 has the same delay as the element of the last row, and the element on row 2 has a similar delay as the second element from the last beginning of the top, and so on. In an embodiment, the delay between adjacent elements in a column is linear. The results in table 1 and the elevation beam pattern in fig. 23 quantify the effect of using a linear delay profile in elevation compared to a parabolic profile. The results in table 1 quantify the beamwidth (at-3 dB and-10 dB) of the unidirectional beam pattern in fig. 21. Five different implementations of elevation focusing were studied for 2D transducer arrays: 1) no elevation focus, 2) perfect 2D focus (equation 4), 3) linear delay, 4) piecewise linear delay, and 5) sparse apodization. For the case of linear delays, the delays between adjacent elements along the column are fixed relative to each other, and the elevation delay profile may be symmetrical about the center of the array. For piecewise linear delays, the delay profile is divided into at least 3 segments, with adjacent elements in a given segment having fixed delays relative to each other. The method may better approximate a parabolic delay profile by including a plurality of linear delay segments. Finally, the sparse apodization method reduces the number of active elements by switching on and off the elements compared to other methods in order to make the array behave like a 1.5D array when transmitting. An example of such a sparse apodization method is shown in figure 21. In this method, the output pressure can be reduced compared to the output pressure of the full aperture. The results in table 1 show-3 dB and-10 dB beamwidths for an elevation beam pattern with an azimuth of 0 ° steering. The results show that the linear delay method is superior to using the elevation-free focusing method and is similar to the perfect 2D focusing method. The piecewise linear delay method achieves even better beamwidth performance than the linear method. The sparse apodization method is superior to the non-elevation focusing method in terms of achievable beam width, but not as linear. The reason why the sparse apodization method performs poorly is likely due to the reduced spacing of the "rows" along the sparse array as compared to other methods. The elevation beam pattern results in fig. 21 show that the linear and piecewise linear delay beam patterns are similar to 2D focused beam patterns as low as-15 dB. The sparse apodization method has an asymmetric beam pattern due to the lateral offset of the rows and the method also exhibits the largest side lobes in all the investigated methods. These methods also demonstrate stability when maneuvered laterally off-axis (right hand diagram of fig. 21). These results indicate that the electronic elevation delay method described above is a suitable alternative to phased and linear array imaging in low cost, battery powered ultrasound systems.

Focusing method	-3dB beam width (mm)	-10dB beamwidth (mm)
			Non-elevation focusing	6.08	15.98
Perfect 2D focus	5.35	9.23
			Linear delay	5.38	9.25
Piecewise linearity	5.35	9.25
			Sparse apodization	5.50	9.65

Table 1: the effect of various delay profiles or no focusing on elevation focusing is used. These results quantify the results of steering the beam pattern at the 0 azimuth on the left hand side of fig. 21.

Fig. 21 shows the elevation beam pattern of a simulated 24x128 matrix array with 0 ° lateral steering (left) and 45 ° lateral steering (right). The figure shows the difference (blue curve) of the method of providing focus in the elevation dimension studied compared to non-elevation focus.

Fig. 22 shows a sparse Tx aperture that allows transmit elevation focusing with a 24x128 2d array. Shadow circles are active elements of each column and elevation symmetry is used (assuming focus along a symmetrical elevation plane). This emission scheme will output about 1/3 less pressure than when using all 24x128 active elements.

In some embodiments, each element on a column has a dedicated transmit driver. In some embodiments, each element driver includes a digital delay circuit driven by a clock (e.g., txB Clk). The delay circuit in one embodiment includes a plurality of flip-flops as shown in fig. 15A. The flip-flops (e.g., DFF1, DFF2, DFF3, DFF4, etc.) have digital inputs starting from the bottom of the column (e.g., row 0). TxA is a digital bit generated by the transmit beamformer. In the preferred embodiment, the transmit beamformer consists of circuitry providing a plurality of digital bits per channel. In fig. 15A, we show 2 bits per lane. TxA is such a bit. TxB is another bit in which the circuit is the same as that shown attached to TxA, as is TxB. The 2 bits are encoded to determine the voltage drive level of the transmit driver as shown in fig. 28. Here, txA and TxB are digital signals decoded to determine the output level of the Tx driver. For example, if TxA, txB are both 0 or, the output level is a common level, sometimes a signal ground level. If txa=l, txb=0, the output is HI. This may be a positive voltage of 5V or 10V or some other value, as desired. When txa=0, txb=l, for example, the output becomes LO or-5V or-10V when the common voltage is 0V. TxA and TxB are created in the Tx beamformer using a high speed clock called TxB CLK. In the preferred example, this clock is a 200MHz clock. The delayed output signal from the Tx pulser output can be used to steer or focus the ultrasound beam as shown in fig. 16. Here, it is assumed that the line imager has all elements on the line that share the same delay. Each line element has 2 bits (TxA, txB) that are transmitted by the Tx beamformer. The bits of the next line are different and may be delayed as needed to steer or focus the beam. These delays imposed by the Tx beamformer are along the azimuth axis and may steer or focus the beam in the axial direction. However, delays are also required in the elevation direction to steer or focus the beam in the elevation plane. This requires a separate delay for the elements on the columns. Fig. 15A shows an exemplary embodiment. The TxA, txB bits arrive at the column from the Tx beamformer. Flip-flops DFF1-DFFN are located in each row, where N is 1 to 16 or 32 or a size as desired. The input pin 2 of DFF1 is connected to TXA or TxB. Pin 1 of the flip-flop is connected to a clock named clk hi, which is generated by a digital divider with the TxB clock as its input. Division is divided by M, with a digital input bus (shown here as an 8-bit bus) labeled Div Control being used to determine the value of M. Flip-flops DFF1-DFFN produce delays of the TxA/TxB input signal as shown in fig. 15A, where A, B, C is a delayed version of TxA, txB. The outputs of these are connected to a MUX that selects one of these inputs as its output, where the selection is done using a DECODER controlled by SEL0, SEL1, etc., where these consist of F bits. These digital outputs, in this case 2 per element, are then decoded, as shown in fig. 20, and used to drive the pulser output. For elements on a column, the circuit may provide a fine delay relative to the input delay on the TxA, txB bits. Furthermore, these delays may be unique to the elements on the columns. Fig. 15B shows an exemplary embodiment in which coarse delays may also be added to the elements on the columns. Here another divider, this time divided by N, inputs clk TxB, where M is less than or equal to N and is an integer. The divider output clk_lo is connected to the clk input of the DFF, as shown in fig. 15B. Here, the output of TxA or DFF (which is a delayed version of TxA) is connected to the MUX and applied to row0 elements if a non-delayed version is selected. Which is then connected to pin 2 of the DFF on row 1. This time, if the row 1 element wants to delay, the delayed version (pin 3 output of the DFF) is selected by the MUX on the first row. This may be repeated for the next element. Here we add delay to all elements on the column except for the element on row 0. This linear delay applied to the column elements will help steer the beam. The circuits on fig. 15A and 15B can also be combined to impart fine and coarse delays to all elements on a column. This may be done, for example, by adding a circuit to int_txa@row0 and similar nodes on other rows, where the fine delay circuit from fig. 15A is inserted to add a fine delay to these outputs that have been delayed by the coarse delay generator. These circuits provide a fine delay. After the output of the DFF, mux is entered, similar to mux1, but for the next row. The signal is then delayed by the DFF to which it is connected. The same process is vertically repeated to the other rows. This will delay the signal linearly along the elements on the columns. On each row, DFF1-DFF N adds a fine delay to all elements on the column as needed. Mux1 and mux-like second inputs for all rows are used to delay the signal linearly, starting with the lowest delay at the top and the highest delay at the bottom (row 0). This TxA/B will also be connected to pin 2 of clone (clone) of the last row mux l. Thus, using the UP control on MUX1 (and equivalent controls on other rows), the delay may increase from bottom to top and vice versa. Fig. 19 shows the pulser waveform, i.e. the output of the transmit driver after the delay and decoding for elevation focusing are completed, where Pl represents the transmit driver output of element 1 with 1 delay unit, P2 represents 2 delay units applied to element 2, and P4 is the output of the element 4 transmit driver with 4 delays. In this case, only the coarse delays on the columns are shown in the figure, and the fine delays are not shown. Fig. 16 shows the relative delays of the elements on the columns. In some embodiments, the delay size determines the focal length. In some embodiments, the start delays for all columns may be different, set according to the need for focusing along the azimuth axis. The delay along the elevation axis may be arbitrary. For example, the delay may increase linearly from bottom row to top row of transducers. In this case, the beam may be steered in the elevation direction. If the delay is symmetrical about the central element, the focus is in the elevation plane. Other various delay profiles are possible and may allow focusing and steering of the elevation slices.

Fig. 17 shows a non-limiting exemplary waveform of transmit drive pulses applied to piezoelectric elements along a column of transducers. In this embodiment, the transducer has 24 piezoelectric elements on the column. P0 is the piezoelectric element on a certain column (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, etc.) on row 0, P1 is the piezoelectric element on the same column as P0 but on row 1, P11 is on the same column but on row 11, P22 is on row 22, and P23 is on row 23. In this embodiment, a pulse of a specific frequency is applied to the element P0. The same pulse is applied to element P1, but delayed by t01 relative to P0. Similarly, the same pulse reaches P11 with a delay t011 longer than the delay t01. In this embodiment, the delay has symmetry around the central element P11. This means that the pulse timings at P23 and P0 are substantially the same, the pulse timings at P1, P22 are substantially the same, and so on, as shown in fig. 17. In some embodiments, the pulses (width, amplitude, shape, and/or frequency) herein are the same for all elements of the same column. In some embodiments, the pulse relative delays and frequencies herein are the same for all elements on both rows in a column, but for an initial delay on an element, the first element in a column may be different from a similar element in a different column. In some embodiments, the pulses herein have various shapes, and the waveform may have multiple pulses. Non-limiting exemplary shapes of the pulses include one or more of rectangular pulses, gaussian pulses, and sinusoidal pulses. In some embodiments, for all elements on all selected columns, delays (e.g. t01, t 02) t03....t 011) is covered. Electronically programming and controlling.

Fig. 18 shows the delay relationship between columns. In this particular embodiment, the delay is determined by the transmit beamformer channel delay. For example, t10 is the delay between element 0 on column 0 and element 0 on column 10. These delays are programmed in the transmit beamformer and are electrically tunable to help align Jiao Boshu in the azimuth plane, as shown by plane xa-za in fig. 10A. In some embodiments, the delays between elements on the columns are individually programmed to focus the beam or tilt the beam in the elevation plane, as shown by plane ya-za in fig. 10A. t01 is an exemplary delay between elements on the same column (e.g., element 0 and element 1 on column 0 and element 1 on column 10). In some embodiments, the delays of the column elements are relative to a starting delay determined by the transmit beamformer of the channel. In some embodiments, the start delay may be predetermined by or adjustable by the transmit beamformer.

Referring to fig. 20, in a particular embodiment, an example of a pulser function is shown. IN this embodiment, two digital inputs, i.e., IN1 (e.g., txA IN fig. 17), IN2 (e.g., txB IN fig. 15A), control the voltage output level of the pulser. Based on the logic levels of these two inputs, a three-level output result may be generated, where HVP0 is a positive high voltage, HVM0 is a negative low voltage, and XDCR is an active level or 0V. In this embodiment, five periods of the same pulse shape are generated as output results. IN some embodiments, the mode, frequency, and/or number of pulses of the output result may be changed by changing the IN1, IN2 mode and/or the frequency of the mode. In some embodiments, the logic levels or logic encodings herein may comprise digital logic operations of one or more inputs. In some embodiments, the logic operations include using one or more logic operators selected from the following for one or more inputs: AND, NOT, OR, NAND, XOR, NOR, XNOR or any other logical operation.

In some embodiments, the series/chain of cascaded flip-flops is gated from the transmit driver for that column to the transmit clock of one or more columns with an appropriate predetermined or preprogrammed delay. In some embodiments, the delay then propagates through the columns by a different clock whose frequency is programmable but synchronized with the transmit clock that generates the delay for the drivers of the various column drivers. In some embodiments, the flip-flop chain that generates the delay stops at the center element of the column, with the delay profile symmetrical about the center, as in fig. 17. The delay generated by the flip-flop may be routed to the appropriate location in one or more columns so that the element on row 0 has the same delay as the element on the last row, the element on row 2 has a similar delay as the 2 nd element from the last on top, and so on.

In an embodiment, elevation focusing is achieved using various delay profiles. The use of a linear delay profile in the elevation direction allows the delays to monotonically increase or decrease from the bottom to the top of the column to steer the beam in the elevation direction. In addition to this, a certain additional curvature to the beam may allow focusing in addition to beam steering, where the curvature at the end of the column is zero. The linear approximation of the theoretical delay required may be accurate enough to provide steering and focusing, and allow for the economic implementation described in the embodiments herein.

Fig. 23 shows a schematic diagram of an mxn array 2000 of piezoelectric elements 2002-11-2002-mn in accordance with an embodiment of the present disclosure. As depicted, each piezoelectric element may be a two-terminal piezoelectric element (such as piezoelectric element 214 in fig. 3A) and have an electrode (O) (e.g., 2003-11) electrically coupled to a conductor (O) (e.g., 2004-11) and an electrode (X) electrically connected to ground or DC bias voltage via a common conductor (X) 2006. In an embodiment, each signal conductor (O) may be independently managed by a circuit element. In an embodiment, each conductor (O) (e.g., 2004-mn) may be electrically coupled to a transmit driver of a circuit element, while all X electrodes (2006-11-2006-mn) of the array of piezoelectric elements may be connected to a common conductor (X) 2006. In an embodiment, the array 2000 may be disposed on a transceiver substrate and electrically coupled to the ASIC chip through an interconnect mechanism (such as m×n+1 bumps). More specifically, the mxn conductors (O) 2004-11-2004-mn may be coupled to the mxn transmit drivers of the ASIC chip by mxn bumps, and the common conductor (X) 2006 may be coupled to the ASIC chip by one bump. In an embodiment, such an exemplary arrangement described herein is used to perform 3D imaging, wherein each piezoelectric element comprising at least one sub-piezoelectric element may provide unique information in the array. In an embodiment, each piezoelectric element may have one or more membranes and vibrate in multiple modes and frequencies of the membranes. In an embodiment, each piezoelectric element 2002 may be driven by a pulse having the voltage profiles 3300 and 3400 in fig. 27 and 28.

In an embodiment, the O electrodes in each column (e.g., 2003-11-2003-m 1) may be electrically coupled to a common conductor. For example, the circuit elements in the ASIC chip may be electronically controlled such that the O-electrodes in each column may be electrically coupled to each other. In this configuration, during the transmit mode, the O electrodes in each column may receive the same electrical pulse through a common transmit driver or through multiple drivers with the same electrical drive signal. Similarly, during the receive mode, the O electrodes in each column may simultaneously transfer charge to the common amplifier. In other words, the piezoelectric elements in each column may operate as a wire unit (or equivalent wire element).

Fig. 24 illustrates an exemplary embodiment of an imaging system 2900 according to an embodiment of the disclosure. As shown, the imaging system 2900 includes an array of piezoelectric elements 2902-11-2902-mn, and each piezoelectric element may include first and second signal (O) electrodes and a T electrode. In an embodiment, all T electrodes in the array may be electrically coupled to one common conductor (T) 2908; each row of first O electrodes may be electrically connected to one of the conductors O1-Om; if a line imager without a synthetic lens is desired, a mechanical lens is sufficient in this case. However, the same function can be achieved by not shorting all O-nodes on a column, as shown in fig. 24. Instead, each O-node is driven by a driver, and if all driver signals for the column elements have the same delay, we achieve essentially the same behavior as shown in fig. 24. In the embodiment shown in FIG. 24, each of the switches 2912-1-2912-n may be switched between a transmit driver (e.g., 2916-1) and an amplifier (e.g., 2914-1), which may be a low noise amplifier. In an embodiment, each of conductors O1-On may be connected to one of amplifiers 2910-1-2910-m, which may be low noise amplifiers.

In an embodiment, during the transmit mode, a signal may be transmitted from the transmit driver (e.g., 2916-1) to the second O-electrode column via a conductor (e.g., O12) such that the column of piezoelectric elements may generate pressure waves as a line element. During a transmit mode, each switch (e.g., 2912-1) may switch to a corresponding transmit driver (e.g., 2916-1).

In an embodiment, imaging system 2900 may process reflected pressure waves in two different ways. In a first approach, the amplifiers 2910-1-2910-n may receive charge signals from a first O electrode, i.e., each amplifier may receive signals from a row of first O electrodes. The method allows for a biplane imaging/mode, wherein for a two-dimensional image, the biplane image may provide orthogonal viewing angles. Furthermore, the method may provide imaging capabilities that are more than two-dimensional. Biplane imaging can be useful for many applications, such as biopsies. Note that in this method, the transmission mode and the reception mode may be performed simultaneously. In a second approach, the switch 2912 may switch to the amplifiers 2914 such that each amplifier may receive and process the charge signal from a corresponding column of the second O electrodes.

In an embodiment, a line cell refers to a column (or row) of O electrodes electrically coupled to an O conductor, which may operate as a transmitting cell or a receiving cell, or both. In an embodiment, even if conductors O1-Om are arranged in directions orthogonal to conductors O12-On2, these directions may be electronically programmed and electronically tunable. For example, the gains of the amplifiers 2910 and 2914 may be electronically adjustable, with gain control leads implemented in the amplifiers. In an embodiment, the length of each wire element (i.e. the number of piezoelectric elements in each wire element) may also be electronically regulated. In an embodiment, this may be achieved by connecting all signal electrodes of each piezoelectric element to corresponding nodes in an ASIC chip, and wherein the ASIC programs the connections between signal electrodes, transmit drivers or amplifiers of the elements to be connected to each other as appropriate.

Fig. 25 illustrates an embodiment of a piezoelectric element 3000 coupled to a circuit element 3001 according to an embodiment of the present disclosure. As depicted, piezoelectric element 3000 may include: a first sub-piezoelectric element 3021-1 and a second sub-piezoelectric element 3021-2. The piezoelectric element 3000 may include: a bottom electrode (X) 3002 shared by the first sub-piezoelectric element and the second sub-piezoelectric element and coupled to conductor (X) 3006. In an embodiment, the first sub-piezoelectric element 3021-1 may include a signal (O) electrode 3003 electrically coupled to the amplifier 3010 via a conductor 3008. In an embodiment, the second sub-piezoelectric element 3021-2 may include a signal (O) electrode 3004 electrically coupled to the switch 3014 via the conductor 3012.

In an embodiment, the circuit element 3001 may be electrically coupled to the piezoelectric element 3000 and include two amplifiers 3010 and 3016 (such as low noise amplifiers) and a transmit driver 3018. In an embodiment, the switch 3014 may be such that one end is connected to the O electrode 3004 by a conductor 3012, and the other end may be switched between an amplifier 3016 for a receive mode and a transmit driver 3018 for a transmit mode. In an embodiment, the amplifier 3016 may be connected to other electronics to further amplify, filter, and digitize the received signal, even though the amplifier is used to symbolically represent the electronics. The transmit driver 3018 may be a multi-stage driver and may produce an output with two or more level signaling. The signaling may be monopolar or bipolar. In an embodiment, the transmit driver 3018 may include a switch that interconnects the driver's input to the driver's output under the electronic control of the driver, which is not explicitly shown in fig. 25. Also not shown is the input signal of the driver 3018, which may be delayed relative to such signal of another element on the same column as shown in fig. 17A to 17D. Similarly, delays for elements located in different columns are also implemented to allow for electronic focusing along the azimuth axis to allow for electronic focusing along the elevation plane.

In an embodiment, the signal of the transmit driver 3018 may be Pulse Width Modulated (PWM), wherein a weighting function may be created on the transmitted ultrasound signal by controlling the pulse width on a per element basis. This may for example perform a window function, wherein the transmit signal is weighted by the window function. In an embodiment, the weighting coefficients may be implemented by varying the duty cycle of the transmit signal, as is done during PWM signal transmission. This operation may allow for transmit apodization in which side lobes of the radiated signal are greatly attenuated, allowing for higher quality images.

In an embodiment, the transceiver array mayTo be disposed in a transceiver substrate and include an n x n array of piezoelectric elements 3000, and an n x n array of circuit elements 3001 may be disposed in an ASIC chip, wherein each piezoelectric element 3000 may be electrically coupled to a corresponding one of the n x n arrays of circuit elements 3001. In this case, the transceiver substrate may pass through 3n ² The bumps are interconnected with the ASIC chip. In an embodiment, each column (or row) of the array of piezoelectric elements may operate as a line unit, as discussed in connection with fig. 25. For example, the same pulse may be applied to a row of piezoelectric elements simultaneously, so that the row of piezoelectric elements may generate pressure waves simultaneously. Note that each piezoelectric element 3000 of the n×n array of piezoelectric elements may be coupled with a corresponding one of the circuit elements 3001 of the n×n array of circuit elements. Alternatively, each element on a column may be controlled separately by connecting the element's O node to a dedicated Tx driver and also to a dedicated receive amplifier. By controlling the delay on the transmit driver and the signal received from the LNA, elevation focusing can be achieved in both the transmit and receive directions.

In an embodiment, the sub-piezoelectric element 3021-1 may be in a receive mode during the entire operation period, and the sub-piezoelectric element 3021-2 may be in a transmit mode or a receive mode. In an embodiment, simultaneous operation of the transmit mode and the receive mode may allow continuous mode doppler imaging.

In an embodiment, when the transmit driver 3018 transmits signals to the electrode 3004, the power level of the pressure wave generated by the sub-piezoelectric elements 3021-2 may be changed by using Pulse Width Modulation (PWM) signal transmission. For example, this is important when switching from B-mode to doppler mode imaging, the signal power transmitted to the human body may be long, and if the power level is not reduced, tissue damage may occur. Typically, in conventional systems, different fast settling power supplies are used for B-mode and various doppler mode imaging to allow the transmit drive voltage to be different in both cases, e.g., without generating excessive power in the doppler mode. Unlike conventional systems, in embodiments, the power level may be changed by using a PWM signal at the time of transmission without using a conventional fast settling power supply. In embodiments, it is desirable to rapidly switch between Doppler and B-mode imaging to jointly image these modes together. In an embodiment, the ground electrodes of the piezoelectric elements may also be separated from each other and individually connected to ground. In embodiments, such independent grounding may reduce noise and result in faster settling times. In an embodiment, the transmit power may also be reduced by reducing the height of the transmit columns under electronic control. This again facilitates the Doppler and B modes to use the same power supply and meets the power transfer requirements in each mode. This also allows for common imaging.

Fig. 26 illustrates a circuit 3100 for controlling a plurality of piezoelectric elements according to an embodiment of the disclosure. In an embodiment, circuit 3100 may be provided in an ASIC chip, wherein an array of piezoelectric elements (arranged in rows and columns) provided in the transceiver substrate and ASIC chip may be interconnected to the transceiver substrate by bumps, wherein each pMUT may be connected to an associated Tx driver and receive circuit by a switch as shown in fig. 25, wherein the O electrode is connected to switch 3014. As depicted, the circuit 3100 can include an array of circuit elements 3140-1-3140-n, where each circuit element can communicate signals with the O-electrode and the X-electrode of a corresponding piezoelectric element.

As shown in fig. 26, each circuit element (e.g., 3140-1) may include a first switch (e.g., 3102-1), a second switch (e.g., 3104-1), a third switch (e.g., 3106-1), and a transmit driver (e.g., 3108-1). The output from the transmit driver (e.g., 3108-1) may be sent via a conductor (e.g., 3110-1) to the O-electrode of the piezoelectric element. During a transmit mode, each circuit element may receive a transmit driver (drive) signal 3124 over conductor 3122. Each second switch (e.g., 3104-1), which may be a transistor switch and controlled by control unit 3150, may be turned on to transmit signal 3124 to the transmit driver (e.g., 3108-1). (electrical connections between the control unit 3150 and other components in the circuit 3100 are not shown in fig. 26.) the transmit driver (e.g., 3108-1) may perform logic decoding, level shifting, buffering the input signal, and sending the transmit signal to the O electrode via the conductor (e.g., 3110-1). In an embodiment, during the transmit mode, the first switch (e.g., 3102-1) may be turned off.

In an embodiment, the control unit 3150 may decide which piezoelectric elements need to be turned on during the transmit mode. If the control unit 3150 decides not to turn on the second piezoelectric element, the first switch (e.g., 3102-2) and the second switch (e.g., 3104-2) may be turned off, and the third switch (e.g., 3106-2) may be turned on, such that the O electrode and the X electrode have the same potential (i.e., there is a net zero volt drive across the piezoelectric layer). In an embodiment, the third switch 3106 may be optional.

In an embodiment, during the receive mode, a first switch (e.g., 3102-1) may be turned on so that charge generated in the O electrode may be transmitted through conductors 3110-1 and 3120 to amplifier 3128. The amplifier 3128 may then receive the charge signal (or equivalently, the sensor signal) 3126 and amplify the sensor signal, where the amplified signal may be further processed to generate an image. During the receive mode, the second switch (e.g., 3104-1) and the third switch (e.g., 3106-1) may be turned off so that the received signal is not disturbed. Note that the entire array of circuit elements 3140-1-3140-n may share a common amplifier 3128, simplifying the design of circuit 3100. In an embodiment, the X electrode of the piezoelectric element may be electrically coupled to ground or DC bias voltage via conductors 3112-1-3112-n, where conductors 3112-1-3112-n may be electrically coupled to common conductor 3152.

In an embodiment, the circuit 3100 may be coupled to a column of piezoelectric elements (e.g., 2002-11-2002-n 1) in fig. 23. In an embodiment, the circuit 3100 may control a column of piezoelectric elements in fig. 25-32.

Fig. 27 and 28 illustrate exemplary waveforms 3300 and 3400 for driving a piezoelectric element during a transmit mode, according to an embodiment of the present disclosure. In general, piezoelectric materials may be susceptible to damage caused by dielectric aging, and aging may be delayed or avoided by using unipolar drive signals. Waveforms 3300 and 3400 represent voltage potentials between O and X electrodes and/or between O and T electrodes. As depicted, the waveform may be unipolar in nature and may be a dual-level step waveform 3300 (i.e., the transmit drivers such as 2812, 2912, 3018, 3108, 3208, etc. are unipolar transmit drivers) or a multi-level (such as three-level) step waveform 3400. The actual voltage amplitude may typically vary from 1.8V to 12.6V. In embodiments, the multi-step waveform 3400 or waveforms with more steps may reduce heating in the piezoelectric element and may be advantageous for use during certain imaging modes (such as doppler or harmonic imaging).

In an embodiment, the pulse frequency in waveforms 3300 and 3400 may vary depending on the nature of the desired signal, and need to include the frequency of the membrane response underneath the pMUT. In embodiments, the waveform may also be a complex signal, such as a linear or non-linear frequency-modulated chirp signal, or other encoded signal using Golay codes.

In an embodiment, the circuitry for driving the piezoelectric element may also be designed such that the emission output from the underlying membrane may be symmetrical in shape. In an embodiment, for each signal pulse in waveform 3300 (or 3400), the rising edge of the pulse may be substantially symmetrical with the falling edge of the pulse relative to the center of the pulse. This symmetry reduces the harmonic content of the transmitted signal, particularly the second harmonic and other even order harmonic signals. In an embodiment, the signal pulses in waveform 3300 (or 3400) may be Pulse Width Modulated (PWM) signals.

Fig. 29 illustrates a transmit drive signal waveform according to an embodiment of the present disclosure. As depicted, the signal 3500 from the transmit driver may be symmetrical and bipolar, i.e., the amplitude (H1) and width (W1) of the peak maximum voltage is the same as the amplitude (H2) and width (W2) of the peak minimum voltage. Further, the slope of the rising edge 3502 is the same as the slope of the falling edge 3504. In addition, the rise time W3 is the same as the fall time W4, where the fall time W4 refers to the time interval between the fall start point and the reference voltage. Further, the rising edge 3506 has the same slope as the rising edge 3502.

During a transmit operation, a transmit driver, such as 3018 in fig. 25, may be driven by an electrical waveform, such as that shown in fig. 27 and 28. Fig. 30 illustrates output signals of various circuits in an imaging assembly according to an embodiment of the present disclosure. In an embodiment, waveform 3602 may be an output signal from a transmit driver (e.g., 3018) and transmitted to a piezoelectric element (e.g., 3000). In an embodiment, since the piezoelectric element may have an inherent bandwidth, it may output a sinusoidal output 3604 at its resonant frequency. If the output of the transmit driver connected to the O-electrode of the piezoelectric element rises very slowly, it may not be able to charge the electrode to the desired final value and thus may result in a low output signal, as shown in waveform 3606, where the final amplitude is less than the amplitude in 3602. On the other hand, if the output signal of the transmit driver is very fast stable, the output signal of the transmit driver has a bandwidth that is larger than the bandwidth limit of the piezoelectric element, and thus the additional energy may be dissipated in the form of heat. Thus, in an embodiment, as shown in waveform 3608, the piezoelectric element may be charged at a rate that causes it to fully charge, but not very quickly. In an embodiment, waveform 3608 represents the voltage potential across the top and bottom electrodes as a function of time, is closer in shape to the output of the transducer, and because of the smaller differences in shape, the input and output signal bandwidths match better, with less thermal energy loss occurring. In an embodiment, the driving impedance of the transmit driver is optimized to reduce energy losses. In other words, the impedance of the transmit driver is designed to optimally drive the piezoelectric element according to the heat dissipation and time constant required for adequate voltage stabilization over the target period of time.

In an embodiment, the imager 126 may use harmonic imaging techniques, where harmonic imaging refers to transmitting pressure waves at the fundamental frequency of the membrane and receiving reflected pressure waves at the second or higher harmonic frequencies of the membrane. In general, images of reflected waves based on secondary or higher harmonic frequencies have higher quality than images of reflected waves based on fundamental frequencies. Symmetry in the transmit waveform may suppress secondary or higher harmonic components of the transmit wave and, therefore, interference of these components with secondary or higher harmonics in the reflected wave may be reduced, thereby improving image quality of harmonic imaging techniques. In an embodiment, waveform 3300 may have a 50% duty cycle in order to reduce secondary or higher harmonics in the transmitted wave.

In fig. 23-24, the array may include a plurality of wire units, wherein each wire unit includes a plurality of piezoelectric elements electrically coupled to each other. In an embodiment, the line cells may be driven with multiple pulses with a phase difference (or equivalent delay). By adjusting the phase, the generated pressure wave can be steered at an angle, which is known as beamforming.

Fig. 31A shows a graph of the amplitude of a transmitted pressure wave as a function of spatial position along the azimuth axis of a transducer, in accordance with an embodiment of the present disclosure. If the piezoelectric elements in the array are arranged in 2 dimensions, and the piezoelectric elements on the columns in the Y direction are connected and have many columns along the X direction, the X direction is referred to as the azimuth direction, and the Y direction is referred to as the elevation direction.

In some embodiments, the apodization herein includes using variable voltage drives, e.g., with lower weights near the edges of the ultrasonic pulses and more sufficient weights near the center portions. Apodization can also be achieved by varying the number of elements along each column or row, alone or in combination with other methods disclosed herein.

Fig. 31B illustrates various types of windows for an apodization process according to embodiments of the present disclosure. In fig. 31B, the x-axis represents the position of the piezoelectric element relative to the piezoelectric element at the center of the active window, and the y-axis represents the amplitude (or weight applied to the piezoelectric element). As depicted, for rectangular window 3720, no weighting is provided for any of the transmit lines, i.e., they are all at a uniform amplitude (i.e., symbolically 1). On the other hand, if a weighting function is implemented, as depicted by hamming window 3722, the line at the center gets a greater weight than the line at the edges. For example, to apply hamming window 3722 to the transducer block, the piezoelectric elements in the leftmost column (denoted as-N in fig. 31B) and the piezoelectric elements in the rightmost column (denoted as N in fig. 31B) may have the lowest weights, while the piezoelectric elements in the middle column may have the highest weights. This process is known as apodization. In an embodiment, various types of window weighting may be applied, even though the illustrated hamming window 3722 is intended as an example only. In an embodiment, apodization can be achieved by a variety of means, such as by employing a digital-to-analog converter (DAC) or by scaling the transmit driver output drive level differently for different lines by maintaining the same drive level but reducing the number of pixels on the line. The net effect is that the sidelobe levels can be reduced by using apodization, wherein the weight of the transmit drive varies based on the position of the particular line within the excited transmit aperture.

In an embodiment, a decrease in the pulse or waveform voltage may decrease the temperature at the transducer surface. Alternatively, for a given maximum acceptable transducer surface temperature, a transducer operating at a lower voltage may provide better detector performance, resulting in better quality images. For example, for a probe having 192 piezoelectric elements to reduce power consumption, the emitted pressure wave may be generated by using only a portion of the probe (i.e., a subset of the piezoelectric elements) and using a multiplexer to scan the remaining elements in time sequence. Thus, at any point in time, in conventional systems, only a portion of the transducer elements may be used to limit the temperature rise. In contrast, in embodiments, a lower voltage detector may allow more piezoelectric elements to be addressed simultaneously, which may enable increased frame rate of images and enhanced image quality. A large amount of power is also consumed in the receive path that amplifies the received signal using the LNA. Imaging systems typically use multiple receive channels, each with an amplifier. In an embodiment, using temperature data, multiple receiver channels may be disconnected to save power and reduce temperature.

In an embodiment, apodization can be achieved by varying the number of piezoelectric elements in each wire unit according to a window function. In embodiments, such window approximation may be achieved by electronically controlling the number of piezoelectric elements on-line or by hard-wiring the transducer array with the desired number of elements. Apodization can also be created by using a fixed number of elements but driving these elements with varying emission drive voltages. For example, for apodization in the elevation direction, the maximum drive is applied to the center element on the column, while the lower driver levels are applied to the outer elements on both sides of the column surrounding the center element on the column. Apodization can also be achieved by changing the polarization intensity of the elements based on the position on the columns.

In general, the amount of heat generated by the probe may be a function of the pulse duration in the transmitted pulse/waveform. In general, a piezoelectric element may require a long pulse train in order for the pressure wave to penetrate deep into the target with a better signal-to-noise ratio (SNR). However, this also reduces the axial resolution and also generates more heat in the piezoelectric element. Thus, in conventional systems, the number of pulses transmitted is very small, sometimes only one or two. Because longer pulses may generate more thermal energy, making their use in conventional systems impractical. In contrast, in an embodiment, pulses and waveforms 3300 and 3400 may have significantly lower peaks, which may enable the use of long bursts, chirps, or other encoded signal transmissions. In an embodiment, longer bursts do not reduce the axial resolution because matched filtering is performed in the receiver to compress the waveform to recover resolution. This technique allows for better signal-to-noise ratio and allows the signal to penetrate deeper into the body and allows for high quality imaging of objects deeper into the body.

In an embodiment, a layer of Polydimethylsiloxane (PDMS) or other impedance matching material may be spin coated over the transducer elements. The layer may improve impedance matching between the transducer element and the human body, and may reduce reflection or loss of pressure waves at an interface between the transducer element and the human body.

In fig. 23 to 24, more than one line unit may be created by connecting pixels in the y-direction (or x-direction), where one line unit (or equivalent line element) refers to a plurality of piezoelectric elements electrically connected to each other. In an embodiment, one or more wire units may also be created by connecting the piezoelectric elements in the x-direction. In an embodiment, the piezoelectric elements in the wire unit may be hardwired.

As shown in fig. 7, each piezoelectric element 260 may be electrically coupled to circuitry such as a transmit pulser, switch, and LNA. The number of piezoelectric elements in the transceiver substrate may be the same as the number of circuits in the ASIC chip that interfaces to the pMUT transducer array. The elements may be arranged in columns or rows and may be electronically selected for connection to an ASIC containing electronic circuitry. For an electronically controlled line imager, the line imager/unit may be constructed by connecting each piezoelectric element of a two-dimensional matrix array to a corresponding control circuit of a two-dimensional array of control circuits, where the control circuits are positioned spatially close to the pixels and contained in an ASIC such as that shown in fig. 32, for example. To create a line element, multiple drivers controlling a column (or row) of pixels may be electronically turned on. In an embodiment, the number of drivers in each line imager/unit may be electronically modified under program control and electronically adjustable.

In an embodiment, the smaller capacitance of each pixel can be effectively driven by the distributed drive circuit without the need for other equalization elements between the driver and the pixel, thereby eliminating the difficulty of driving very large line capacitances. In an embodiment, driver optimization may allow for symmetry of rising and falling edges, allowing for better linearity in the emission output, enabling harmonic imaging. (symmetry is described in connection with fig. 27 and 28.) in embodiments, electronic control may allow programmable aperture size, emission apodization, and horizontal or vertical steering control, all of which may improve image quality. In an embodiment, the configurable line imager/unit under electronic control may be electrically modified under program control. For example, if a smaller number of connection elements is required in the y-direction, this number can be adjusted by software control without having to re-rotate the control electronics or the piezoelectric array.

In an embodiment, each line unit may be designed to consist of several sub-units, each with separate control. An advantage of these sub-units is that they can alleviate the difficulty of driving large capacitive loads of the line units using a single external transmit driver. For example, if two wire units are created instead of one wire unit including the entire piezoelectric element in the column, two different emission drivers may be employed, and each emission driver may control half of the load of the entire wire unit. Further, even if one driver is used, the front half of the line unit and the rear half of the line unit are individually driven, and the driving condition can be improved due to the lower resistance connection to both ends of the line unit.

In an embodiment, both the length and the orientation of the wire units may be controlled. For example, the line cells may be arranged in both the x and y directions. For example, in fig. 23, O electrodes along a column (e.g., 2003-11-2003-n 1) may be electrically coupled to form one line cell, and O electrodes in other columns may be electrically coupled to form n line cells extending along the x-direction. More specifically, the line unit extending along the x-direction includes n O electrodes (2003-12-2003-1 n) &... In an embodiment, it may be possible to achieve an arrangement of line elements along orthogonal directions by controlling circuitry in an ASIC chip.

The transducer array may be made of elements such as those shown in fig. 3B or fig. 3C. In fig. 3C, each element may have one or more sub-elements, where each sub-element has a membrane disposed under a piezoelectric layer. In embodiments, these membranes may have multiple modes of vibration. In an embodiment, one membrane may vibrate in a fundamental mode at a particular frequency, while the other membrane may vibrate at a different frequency determined by the membrane design. This enables the element to operate over a wide frequency range while still requiring only 2 terminals. In other embodiments, such as in fig. 3B, the subelements can have separate drive terminals. By using the drive signal content in different frequency regions, a wider bandwidth can be obtained using different drive signals for each subelement. This also allows the output signal to be regulated by using a plurality of sub-elements, each having a different drive signal. One such application is the use of drive signals designed to cancel crosstalk from neighboring elements. In an embodiment, multiple membranes may be driven by the same electrode set, and each membrane (subelement) may have a different fundamental frequency. In an embodiment, each membrane may be responsive to a wide range of frequencies, thereby increasing its bandwidth.

In some embodiments, the X (or T) electrodes in a column may be electrically coupled to a conductor. In embodiments, these conductors may be electrically coupled to a common conductor. For example, the conductors may be electrically coupled to a common wire such that all T electrodes in the array may be connected to ground or a common DC bias voltage.

In some embodiments, each array may include piezoelectric elements (e.g., fig. 23-24) arranged in a two-dimensional array, where the number of elements in the x-direction may be the same as the number of elements in the y-direction. However, it will be apparent to those of ordinary skill in the art that the number of elements in the x-direction may be different from the number of elements in the y-direction.

In an embodiment, the ASIC chip coupled to the transducer substrate may contain a temperature sensor that measures the surface temperature of the human body facing imaging device 120 during operation. In an embodiment, the maximum allowable temperature may be adjusted, and the adjustment may limit the function of the imaging device, since the temperature should not rise beyond the upper allowable limit. In an embodiment, this temperature information may be used to improve image quality. For example, if the temperature is below the maximum allowable limit, additional power may be dissipated in the amplifier to reduce its noise and improve the system signal-to-noise ratio (SNR), thereby improving image quality.

In an embodiment, the power consumed by the imaging device 126 increases as the number of line units that are simultaneously driven increases. It may be necessary to drive all of the line elements in the imaging device 126 to complete the emission of pressure waves from the entire bore. If only a few line elements are driven to transmit pressure waves, waiting for a reflected echo to be received at a time, more time is required to complete one cycle of driving the entire line elements of the entire aperture, thereby reducing the rate at which images can be taken per second (frame rate). To increase this rate, more line cells need to be driven at a time. In an embodiment, the information of temperature may allow the imaging device 120 to drive more lines to increase the frame rate.

In some embodiments, each piezoelectric element may have one bottom electrode (O) and one or more top electrodes (X and T), and have more than one resonant frequency.

In an embodiment, the charge generated during the receive mode is transferred to an amplifier, such as 2910, 2914, 3010, 3016, 3128, and 3806. The amplified signal may then be further processed by various electrical components. Thus, it should be apparent to one of ordinary skill in the art that each of the amplifiers 2910, 2914, 3010, 3016, 3128, and 3806 are collectively referred to as one or more electrical components/circuits that process the charge signal, i.e., each amplifier symbolically represents one or more electrical components/circuits for processing the charge signal.

Fig. 32 shows a schematic diagram of an imaging assembly 3800 according to an embodiment of the disclosure. As depicted, imaging component 3800 can include: a transceiver substrate 3801 having a piezoelectric element (not shown in fig. 32); an ASIC chip 3802 electrically coupled to the transceiver substrate 3801; a receiver multiplexer 3820 electrically coupled to the ASIC chip 3802; a receiver Analog Front End (AFE) 3830; a transmitter multiplexer 3824 electrically coupled to the ASIC chip 3802; and a transmit beamformer 3834 electrically coupled to the second multiplexer 3824. In an embodiment, the ASIC chip 3802 may include a plurality of circuits 3804, the plurality of circuits 3804 being connected to the transceiver substrate 3801 and configured to drive a plurality of piezoelectric elements in the transceiver substrate 3801. In an embodiment, each circuit 3804 may include a receiver amplifier (or simply amplifier) 3806 such as an LNA, and a transmit driver 3808 for transmitting signals to the piezoelectric element, and a switch 3810 that switches between the amplifier 3806 and the transmit driver 3808. The amplifiers may have programmable gain and means to connect them to the piezoelectric element that needs to be sensed. The transmit driver has means to optimise its impedance and means to connect to the piezoelectric element to be driven.

In an embodiment, the receiver multiplexer 3820 may include a plurality of switches 3822 and the receiver AFE 3830 may include a plurality of amplifiers 3832. In an embodiment, each of the switches 3822 may electrically connect the circuit 3804 to the amplifier 3832/electrically disconnect the circuit 3804 from the amplifier 3832. In an embodiment, the transmitter multiplexer 3824 may include a plurality of switches 3836, and the transmit beamformer 3834 may include a plurality of transmit drivers 3836 and other circuitry not shown for controlling the relative delays between the transmit driver waveforms of the various drivers, as well as other circuitry not shown for controlling the frequency and number of pulses of each of the transmit drivers. In an embodiment, each of the switches 3826 is turned on and connected to the circuit 3804 during a transmit operation, while the switch 3822 is turned off, while the switch 3810 is connected to the transmit driver 3808. Similarly, during a receive operation, switch 3826 is off and switch 3822 is on, while switch 3810 is connected to amplifier 3806.

In an embodiment, the switch 3810 may switch to the transmit driver 3808 during a transmit mode and to the amplifier 3806 during a receive mode. In an embodiment, a portion of the switch 3822 may be closed such that the corresponding circuit 3804 may be set to a receive mode. Similarly, a portion of the switch 3826 may be closed such that the corresponding circuit 3804 may be set to a transmit mode. Because a portion of switch 3822 and a portion of switch 3826 may be closed simultaneously, the imager assembly may operate in both a transmit mode and a receive mode simultaneously. In addition, the receiver multiplexer 3820 and the transmitter multiplexer 3824 reduce the number of ASIC pins. In an embodiment, the receiver multiplexer 3820, the receiver AFE 3830, the transmitter multiplexer 3824, and the transmitter beamformer 3834 may be included in the circuit 202a, or portions may also reside in 215a in fig. 1B.

In an embodiment, each piezoelectric element may have more than two electrodes, one of which may be in a transmit mode to generate pressure waves and the other of which may be in a receive mode simultaneously to generate charge. This simultaneous operation of the transmit mode and the receive mode allows for better Doppler imaging.

Movement of the imaged object may cause errors in the resulting image and it may be desirable to reduce these errors. One example of movement is when cardiac imaging is performed, the cardiac tissue is moving. A high frame rate may be desirable to reduce the effects of movement. Thus, it may be important to increase the frame rate while maintaining electronic azimuth and elevation focus and apodization. This not only reduces blurring in the image, but also allows for the receiver to be in place by electronically changing azimuth and electronic focus as a function of depthDynamic focusing is used to obtain a better image. By simultaneously operating the top portion and the bottom portion, the number of operations can be reduced, and an increase in frame rate can be achieved in the dual-stage beamformer shown in fig. 14. Furthermore, by completing the scan of one complete column (e.g., A1, B1, and C1 of FIG. 12) before A2, B2, C2 are generated, the effect of on-line movement is facilitated to be minimized. Further, one scan line can be created by using the transmission and reception of all rows and columns in the operated portion. However, using a parallel beamformer technique [ Tore Gru ner ] A plurality of (e.g. 4) beams may be generated in the "High frame rate ultrasound imaging using parallel beamforming" doctor's article of the principles of the philosophy, developed in the university of norway science and technology, 1 month 2009. This may help to further increase the frame rate and reduce the impact of movement. These techniques may also produce aberrations, but there are known electronic methods to correct them.

It may be desirable to output greater pressure levels (without exceeding regulatory limits) to improve image quality. The value of equalization is an increase in pressure output in the frequency region of interest. This increase in pressure output results in a greater signal output, which results in improved signal-to-noise ratio and improved penetration of the tissue by the signal, thereby improving imaging depth. pmuts have high capacitance, increasing the inductance in series with them can help reduce reactance, better match driver impedance, to help increase power transfer.

Fig. 33-37 illustrate transducer arrays and circuits that may be arranged in columns (and rows) and used to transmit and receive ultrasound beams. Uniquely, the inductor is in the current path through the transducer and through the inductor to virtual ground (bias voltage). The addition of an inductor in series with the transducer helps to compensate for the capacitive component of the transducer impedance and helps to match the driver (at node O in fig. 36A) to the impedance of the transducer and helps to maximize power transfer to the transducer. The transmit driver directly drives the transducer with the inductor in the ground loop (or bias loop leg of the transducer). In the present disclosure, the value of the inductors (e.g., about 0.5 μh) cannot enable these inductors to be used in a low frequency region (e.g., 2 MHz) because the area required for each inductor is very large and the number of inductors is also large. The placement of the inductors in the ground loop allows the inductors to be off-chip with a minimum increase in the number of additional pins (one for each inductor). To implement an inductor in series with the driver, two pins are required for each inductor to implement an off-chip implementation.

Fig. 33C shows an example of using inductor-based equalization using a legacy technique that adds an inductor in series with the transmit driver. Here, D0 is the emission driver. The output of the driver is connected off-chip to pin P0A. An external inductor L0 is connected, the other terminal of the inductor being connected to pin P0B and back to the circuit driving the transducer CO, wherein the other terminal of C0 is connected to pin X0 for connection to a bias voltage. One problem with this technique is that each inductor requires an additional pin P0A, P B. Interconnect routing is also important. Additionally, the driver output is output on pins, exposed to parasitic loads, degrading the performance of the driver. For a 128 channel imager that requires 128 inductors, 256 additional pins would be required, which makes it a great burden or impractical. Furthermore, the amount of interconnects will be greatly increased compared to the subject matter described herein. This is particularly important because the current level is high and in order to keep the impedance similar, the size of the interconnect needs to be increased. The length of the interconnect is doubled due to the need for two separate wires. Thus, it is not practical to integrate equalization techniques using this legacy technology. In fig. 33D a different technique is disclosed whereby the inductor on the other side of the transducer (in series between the transducer and the bias voltage) is moved, requiring only one extra pin and one extra interconnect wiring, making an integrated equalization technique viable. In fact, in many cases, since pins X0, X1 are tp pins, there is little loss in adding an inductor for equalization compared to the situation where there is no inductor-based equalization. The transposition of the inductor on the other side of the transducer not only has the advantages described, but additionally maintains the ability of the circuit to perform equalization. Notably, the circuit also retains the ability to focus in both the azimuth and elevation directions, with focus control being dynamic, as disclosed herein. The piezoelectric element circuit includes an inductor that allows the circuit to be configured to transmit a maximum amount of power in the ultrasound beam. Devices that use inductors within the circuit are integrated in such a way that they do not take up much space and that the circuit is easy to build and use.

Fig. 33A shows a circuit containing a piezoelectric element, which may be part of an array of piezoelectric elements. The array of piezoelectric elements may, for example, contain 4096 piezoelectric elements arranged in a grid of 128 columns and 32 rows and may be used to form a particular emitted ultrasound beam with dynamic focusing. Individual elements in the array of piezoelectric elements may receive signals that are delayed in time in order to alter the focus of the emitted ultrasound beam. The terms "piezoelectric element" and "pMUT transducer element" are used interchangeably herein. In addition, the terms "piezoelectric element circuit" and "pMUT transducer circuit" may also be interchanged.

The circuit of fig. 33A shows the piezoelectric element and its O-and X-nodes and digital input drive. The O-node may designate an input terminal for transmitting a drive signal from the digital input drive to the piezoelectric element. The X node may be a bias or ground node. In the embodiment of FIG. 33A, the X node is biased at-18V, but may be biased at other voltages such that it is more negative than the maximum negative drive voltage on the O node.

In the embodiment of fig. 33A, the piezoelectric element may be highly capacitive and represented as a capacitor in order to correctly identify its behavior as a circuit element. The drive signal provided by the digital input drive may be, for example, a square wave, a step wave, a sine wave, a triangular wave, or another type of alternating voltage signal. For a particular piezoelectric element, the digital input drive may delay a particular signal provided to the piezoelectric element. The amount of time delay may be determined by the placement of the piezoelectric elements within the array and may involve indexing the tag with the numbered rows or columns of piezoelectric elements.

Fig. 33B shows a modification to the circuit of fig. 33A, in which an inductor is connected in series between a piezoelectric element and an X bias node. The inductor may be connected to correct for phase shift introduced by the complex impedance of the capacitive piezoelectric element. The elimination of the phase shift is performed by connecting inductors to increase power transfer by performing impedance matching. For lower imaging frequencies (such as the 1-10MHz region), it is not practical to integrate the inductor with other circuitry on the chip. This is due to the size and number of inductors required on the chip. As the frequency increases (e.g., in the range of 50MHz-100 MHz), the size of the inductor becomes smaller. Therefore, it becomes more practical to integrate the inductor in the chip. Today, most commercial medical imaging applications are below 10MHz in frequency. Because in practice it may be difficult to integrate the inductors for these applications, in one embodiment, external inductors are used to connect the integrated circuit with a matrix array of transmit and receive circuits connected to the matrix array of transducers. Fig. 33A shows one terminal of the transducer connected to a bias voltage (similar to a ground reference). An external inductor is connected between the transducer and the bias terminal. This only requires one pin to be added to each inductor, since the other terminal (X bias is a common pin, already available). This arrangement allows inductor-based equalization. For example, for a matrix array arranged in 128 columns and 32 rows, 128 inductors may be sufficient, with the elements on the columns selected as desired (as shown in fig. 34, by using switches under program control).

Fig. 34 shows a column of N piezoelectric element circuits of the type shown in fig. 33B, connected to a common inductor placed in series between the piezoelectric elements (parallel to each other) and the X bias terminal. In this embodiment, the N piezoelectric elements have N corresponding digital input drives. In other embodiments, for example, if the piezoelectric elements are configured to emit signals with equal delays, the equivalent of one input drive may be used to drive multiple piezoelectric elements. In another example, the transducer drive signals may be delayed relative to each other to achieve electronic focusing in the elevation direction, as explained in fig. 15-19. Multiple piezoelectric elements may be selected at a time from the group and may be deselected or disconnected by opening a switch connecting the piezoelectric elements to the inductor and X bias terminal. The value of the inductor may be chosen to be large enough to counteract the phase change introduced by the capacitance of the piezoelectric element. For example, if 32 piezoelectric elements are electronically selected, the column capacitance may be 1000pF and the inductance of the inductor may be 0.5 μH. Using these inductances to compensate for the capacitance can selectively increase the system bandwidth at certain frequencies. For example, the pressure output may be increased over a certain bandwidth (e.g., 1MHz-6 MHz), while the pressure at higher frequencies (e.g., >10 MHz) may be decreased.

Fig. 35 shows a multi-column piezoelectric element circuit of the type shown in fig. 33A, which does not have an inductor connected between the piezoelectric element and the X bias terminal. The embodiment of fig. 35 shows two columns, but there may be 128 columns in a 4096 array of piezoelectric elements, each with 32 piezoelectric elements. Larger column and row sizes are also possible or practical, as determined by the application requirements, while still falling within the scope of the present disclosure. The two columns shown have emission drives that are delayed relative to each other to allow electron focusing in the azimuthal direction. Additional inductors similar to those shown in fig. 34 allow for similar focusing functions and are shown in fig. 36B. Note that in some applications where the inductor value does not need to be changed, a shorting switch may not be needed.

Fig. 36A shows an embodiment with multiple columns connected to a common X bias line. In the embodiment of fig. 36A, there are multiple columns with multiple inductors. A shorting switch may be used to short the inductor. This is because, at the high frequency of the driving signal, the frequency band of the inductor limits the imager, reduces the ultrasonic pressure output from the transducer, and may reduce the image quality, in parallel with the short-circuited capacitor. In another embodiment, when the inductor can be integrated on an ASIC with other circuitry using a switching arrangement, it will be feasible to select the value of the required inductor. The switching arrangement will have N inductors instead of each inductor as shown for example in fig. 34. The N inductors will have a common terminal and the other terminal will have a switch connected in series with the other end of the switch connected together as shown in fig. 36B. When the switch is open, the diode shunts current flowing into the inductor. This arrangement will allow the value of the inductor to be programmed and electronically adjusted to match the desired impedance. Fig. 37 shows an arrangement of inductors that can be electronically switched to change the value of the inductors. The circuit has two inductors L0 and L1 connected in parallel between terminals T0 and T1. Each inductor has a switching arrangement such as represented by SA0 and SB 0. While the inductor remains in the circuit, SA0 is on, SB0 is off, and vice versa. The switches are logically synchronized to complement each other. Such a composite inductor may replace each of the inductors shown in fig. 36B, for example.

In some embodiments, although the electronic or electrical connections between the various elements shown in the figures herein are hardwired or physical connections, different digital connections may be used to implement programmable and more flexible digital communications. In some embodiments, such digital connections may include, but are not limited to, switches, plugs, gates, connectors, and the like.

While certain embodiments and examples have been provided in the foregoing description, the inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses, and modifications and equivalents thereof. Therefore, the scope of the appended claims is not to be limited by any particular embodiment described. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable order and are not necessarily limited to any particular disclosed order. Various operations may be described as multiple discrete operations in sequence in a manner that is helpful in understanding certain embodiments; however, the order of description should not be construed as to imply that these operations are order dependent. Additionally, the structures, systems, and/or devices described herein may be embodied as integrated components or as stand-alone components.

For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not all of these aspects or advantages may be achieved by any particular embodiment. Thus, for example, various embodiments may be performed in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may be taught or suggested herein.

As used herein, a and/or B encompass one or more of a or B, and combinations thereof, such as a and B. It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions and/or sections, these elements, components, regions and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region or section from another element, component, region or section. Thus, a first element, component, region or section discussed below could be termed a second element, component, region or section without departing from the teachings of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," or "includes" and/or "including" when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

As used in this specification and the claims, unless otherwise indicated, the terms "about" and "approximately" or "approximately" refer to a variation of less than or equal to +/-0.1%, +/-1%, +/-2%, +/-3%, +/-4%, +/-5%, +/-6%, +/-7%, +/-8%, +/-9%, +/-10%, +/-11%, +/-12%, +/-14%, +/-15% or +/-20% of a value, depending on the embodiment. As non-limiting examples, about 100 meters represents a range of 95 meters to 105 meters (which is +/-5% of 100 meters), 90 meters to 110 meters (which is +/-10% of 100 meters), or 85 meters to 115 meters (which is +/-15% of 100 meters), according to an embodiment.

While preferred embodiments have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Many variations, changes, and substitutions will now occur to those skilled in the art without departing from the scope of the disclosure. It should be understood that various alternatives to the embodiments described herein may be employed in practice. Many different combinations of the embodiments described herein are possible and such combinations are considered to be part of the present disclosure. Additionally, all features discussed in connection with any one embodiment herein may be readily adapted for use in other embodiments herein. The following claims are intended to define the scope of the present disclosure and to cover methods and structures within the scope of these claims and their equivalents.

Claims

1. An ultrasound imaging system including a transducer, comprising:

a) At least one transducer element, wherein each transducer element has two terminals, wherein the at least one transducer element is in a transmit mode;

b) At least one transmit driver, wherein each transmit driver is connected to each first terminal of the at least one transducer element; and

c) At least one inductor comprising two terminals, wherein each first terminal of each inductor is connected to each second terminal of each transducer element, wherein each second terminal of each inductor is connected to a bias voltage.

2. The ultrasound imaging system of claim 1, wherein the transducer is a piezoelectric micromachined transducer (pMUT) device, a capacitive micromachined ultrasound transducer (cMUT) device, or a bulk piezoelectric transducer.

3. The ultrasound imaging system of claim 1, wherein the at least one transducer element is a plurality of transducer elements organized in an array, wherein the array is organized in rows and columns, wherein a plurality of transducer elements in a column are electronically selected to define a column of transducer elements, and wherein a plurality of transducer elements in a row are electronically selected to define a row of transducer elements.

4. The ultrasound imaging system of claim 3, wherein the delays of the transducer elements in the first column are independent of the delays of the transducer elements in the second column, and the delays of the transducer elements in the first row are independent of the delays of the transducer elements in the second row.

5. The ultrasound imaging system of claim 3, wherein the transducer elements on a column have different delays.

6. The ultrasound imaging system of claim 3, wherein the bandwidth of the transducer increases in a region of interest.

7. The ultrasound imaging system of claim 3, wherein at least one value of the at least one inductor is selected to provide pressure output adjustment over a frequency range of interest, and wherein the pressure output adjustment is generated by varying a plurality of voltage drive levels of a plurality of transmit drivers of a selected transducer element.

8. The ultrasound imaging system of claim 3, wherein at least one value of the at least one inductor is selected to be large enough to cancel a phase change introduced by at least one capacitance of the at least one transducer element.

9. The ultrasound imaging system of claim 7, wherein the voltage drive level is varied using multi-level transmit drive pulses and selecting a desired digital drive level.

10. The ultrasound imaging system of claim 9, wherein the voltage drive level is also controlled using pulse width modulation of a transmit pulser waveform.

11. The ultrasound imaging system of claim 5, wherein the transducer is configured to provide electronic control of elevation focus in an elevation direction along the column.

12. The ultrasound imaging system of claim 9, wherein the transducer elements along the column are driven by multi-level pulses, and wherein a delay of the start of the multi-level pulses is electrically programmable.

13. The ultrasound imaging system of claim 12, wherein the transducer elements on a column are driven by a multi-level pulse train, and wherein pulse amplitudes, widths, shapes, pulse frequencies, and combinations thereof of multi-level pulses in the multi-level pulse train are electrically programmable.

14. The ultrasound imaging system of claim 12, wherein delays of elements indexed by row and column are calculated by summing delays of the column with delays of the row.

15. The ultrasound imaging system of claim 12, wherein the delay can be a sum of a coarse delay and a fine delay.

16. The ultrasound imaging system of claim 12, wherein the delay of the start of the pulse is programmable in the X-direction and in the Y-direction.

17. The ultrasound imaging system of claim 3, wherein the transmit driver is configured to drive the one or more transducer elements along a column, wherein the transmit driver is driven by signals from transmit channels, wherein the signals of the transmit channels are electronically delayed relative to delays applied to other transmit channels driving other transducer elements on different columns.

18. The ultrasound imaging system of claim 17, wherein one or more transducer elements along the column operate with substantially the same delay.

19. The ultrasound imaging system of claim 17, wherein the transmit channel and additional transmit channels are configured to electrically control relative delays between adjacent columns, and wherein the control circuit is configured to set the relative delays of a first number of transducer elements on the columns such that the first number of transducer elements in a same row shares substantially the same relative delays as a second number of transducer elements of an initial row.

20. The ultrasound imaging system of claim 3, wherein the transducer elements of the plurality of transducer elements comprise a top portion, a center portion, and a bottom portion, each portion comprising a plurality of rows and columns for receipt of pulsed transmitted and reflected ultrasound signals, wherein receipt of pulsed transmitted and reflected ultrasound signals from the top portion, the center portion, and the bottom portion is used to focus the reflected ultrasound signals in an azimuth direction using a first beamformer, and wherein elevation focusing is achieved using a second beamformer.

21. The ultrasound imaging system of claim 20, wherein the focal length in the elevation direction is electronically programmed.

22. The ultrasound imaging system of claim 20, wherein the pulsed emission of the top portion and the bottom portion and the receipt of the reflected signal are performed simultaneously.

23. The ultrasound imaging system of claim 6, wherein two adjacent transducer elements on one of the one or more rows are addressed together, and wherein the transducers of the plurality of transducer elements comprise a top portion, a center portion, and a bottom portion, each portion comprising a first number of rows and a second number of columns for reception of ultrasound signals for transmission and reflection of ultrasound pulses, wherein reception of ultrasound signals from the portions of ultrasound pulses transmission and reflection is used to focus the reflected ultrasound signals in an azimuth direction using a first beamformer, wherein elevation focusing is achieved using a second beamformer, wherein for B-mode imaging, a receive channel is assigned to two transducer elements on the same row, one of the two transducer elements is from the top portion, another transducer element is from the bottom portion, and another channel is assigned to two transducer elements of the center portion, wherein 2N receive channels are used to address N columns.

24. The ultrasound imaging system of claim 23, wherein all of the plurality of transducer elements electronically selected are operated on to generate pressure with elevation focus in a transmit operation, and wherein all of the plurality of transducer elements electronically selected individually are used to reconstruct an image with focus in the azimuth direction and elevation plane in a receive operation.

25. The ultrasound imaging system of claim 5, further comprising a control circuit configured to electrically control the relative delays along a column as a sum of a linear delay and any fine delay, wherein the linear delay and any fine delay of the column are independent of other linear delays and any fine delays of other columns of the transducer, thereby allowing arbitrary steering and focusing in three dimensions.

26. An ultrasound imaging system including an ultrasound transducer, comprising:

a) A bias voltage; and

b) A column of transducer circuits, wherein the transducer circuits comprise:

i) A transducer element comprising a transducer for converting an electrical signal into an ultrasonic wave, wherein the transducer element has a first terminal and a second terminal;

ii) a circuit comprising an input drive device for providing an electrical potential to the transducer element, the input drive device being connected to the first terminal of the transducer element;

iii) An inductor connected to the second terminal of the transducer element; and

iv) a switch for connecting the transducer circuit to the bias voltage.

27. The ultrasound imaging system of claim 26, wherein the ultrasound transducer comprises a plurality of columns, and wherein one of the plurality of columns includes an inductor connected in series with the transducer element, further comprising an inductor connected in series between the plurality of columns and the bias voltage of the transducer circuit.

28. A method for increasing the pressure of ultrasonic waves emitted by a transducer comprising at least one transducer element, comprising:

a) Placing the at least one transducer element in a transmit mode using at least one transmit driver connected to the at least one transducer element, wherein each transducer element has a first terminal and a second terminal;

b) For at least one inductor, connecting a first terminal of each of the at least one inductor to the second terminal of each transducer element, wherein a second terminal of the at least one inductor is connected to a bias voltage, wherein the at least one inductor is not integrated with the transducer element; and

c) Each of the at least one transmit driver is connected to each first terminal of each of the at least one transducer element.